User-input systems and methods of delineating a location of a virtual button by haptic feedback and of determining user-input

ABSTRACT

A system for delineating a location of a virtual button by haptic feedback includes a cover layer, a touch-input sub-system, a haptic transducer, and a haptic controller. The touch-input sub-system includes force-measuring and touch-sensing integrated circuits (FMTSICs), each coupled to the inner surface of the cover layer corresponding to one of the virtual buttons. The touch-input sub-system is configured to determine: (1) supplemental haptic feedback commands if “PMUT Triggered” Boolean data is True for at least one of the FMTSICs (Touched FMTSICs) and light-force conditions are satisfied for all of the Touched FMTSICs, and (2) primary touch inputs if “PMUT Triggered” Boolean data is True for at least one of the FMTSICs (Touched FMTSICs) and light-force conditions are not satisfied for at least one of the Touched FMTSICs. The haptic controller is configured to drive the haptic transducer to generate haptic feedback in accordance with the supplemental haptic feedback commands.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application claims the benefit of U.S. Provisional PatentApplication No. 63/123,914 filed on Dec. 10, 2020, entitled USER-INPUTSYSTEMS AND METHODS OF DELINEATING A LOCATION OF A VIRTUAL BUTTON BYHAPTIC FEEDBACK AND OF DETERMINING USER-INPUT, which is incorporatedherein by reference in its entirety.

BACKGROUND

Recent progress in integration of micro-electro-mechanical systems(MEMS) fabrication technologies with complementarymetal-oxide-semiconductor (CMOS) semiconductor processing have enabledthe fabrication of integrated circuits (ICs) containing piezoelectricmicromechanical ultrasonic transducers (PMUTs) and piezoelectricmicromechanical force-measuring elements (PMFEs). The resulting IC canbe configured to have touch-sensing and force-measuring capabilities.Such ICs can be called force-measuring and touch-sensing integratedcircuits (FMTSICs). A touch-input system can include multiple FMTSICswith each FMTSIC corresponding to one of a plurality of virtual buttons.It would be desirable to enhance the functionality of touch-inputsystems and other user-input systems.

SUMMARY OF THE INVENTION

In one aspect, a user-input system includes: a touch-input sub-systemincluding a cover layer, having an outer surface which can be touched bya finger and an inner surface opposite the outer surface, and aplurality of force-measuring and touch-sensing integrated circuits(FMTSICs), a haptic transducer vibrationally coupled to the cover layer,and a haptic controller coupled to the touch-input sub-system. Each ofthe FMTSICs is coupled to the inner surface at a respective position andeach of the FMTSICs corresponds to one of a plurality of virtualbuttons. Each of the virtual buttons corresponds to a respective regionof the cover layer. Each FMTSIC includes: a semiconductor substrate,signal processing circuitry on the semiconductor substrate, at least onepiezoelectric micromechanical force-measuring element(s) (PMFE(s)), atleast one piezoelectric micromechanical ultrasonic transducer (PMUT)configured as a transmitter (PMUT transmitter), and at least one PMUTconfigured as a receiver (PMUT receiver). The PMUT transmitters of eachof the FMTSICs are configured to transmit ultrasound signals towards thecover layer. The PMUT receivers of each of the FMTSICs are configured tooutput voltage signals (PMUT voltage signals) in response to reflectedultrasound signals arriving from the cover layer. The PMUT voltagesignals are converted to PMUT digital data at the signal processingcircuitry. The PMFEs of each of the FMTSICs are configured to outputvoltage signals (PMFE voltage signals) in accordance with a time-varyingstrain at respective portions of a piezoelectric layer at the respectivePMFEs resulting from a low-frequency mechanical deformation. The PMFEvoltage signals are converted to PMFE digital data at the signalprocessing circuitry of the respective FMTSIC.

In another aspect, the user-input system delineates a location of avirtual button by haptic feedback. The touch-input sub-system isconfigured to: (1) supplemental haptic feedback commands if “PMUTTriggered” Boolean data is True for at least one of the FMTSICs (TouchedFMTSICs) and light-force conditions are satisfied for all of the TouchedFMTSICs, and (2) determine primary touch inputs and optionally determineprimary haptic feedback commands if “PMUT Triggered” Boolean data isTrue for at least one of the FMTSICs (Touched FMTSICs) and light-forceconditions are not satisfied for at least one of the Touched FMTSICs.The haptic controller is configured to drive the haptic transducer togenerate haptic feedback in accordance with the primary haptic feedbackcommands and the supplemental haptic feedback commands. Haptic feedbackgenerated in accordance with supplemental haptic feedback commandsdelineates a location of at least one of the virtual buttons. Thelight-force conditions of each of the FMTSICs include: the PMFE digitaldata of the respective FMTSIC indicates an applied force less thanF_(light). The “PMUT Triggered” Boolean data are obtained from the PMUTdigital data.

In yet another aspect, the user-input system delineates a location of avirtual button by haptic feedback. The user-input system additionallyincludes a processor, coupled to the touch-input sub-system. The hapticcontroller is coupled to the processor and optionally coupled to thetouch-input sub-system. The touch-input sub-system or the processor isconfigured to: (1) determine supplemental haptic feedback commands if“PMUT Triggered” Boolean data is True for at least one of the FMTSICs(Touched FMTSICs) and light-force conditions are satisfied for all ofthe Touched FMTSICs, and (2) determine primary touch inputs andoptionally determine primary haptic feedback commands if “PMUTTriggered” Boolean data is True for at least one of the FMTSICs (TouchedFMTSICs) and light-force conditions are not satisfied for at least oneof the Touched FMTSICs.

In yet another aspect, the user-input system includes another inputsub-system and a processor coupled to the touch-input sub-system and tothe other input sub-system. The haptic controller is coupled to theprocessor and optionally coupled to the touch-input sub-system. Thetouch-input sub-system or the processor is configured to: (1) determinezeroth supplemental touch inputs if “PMUT Triggered” Boolean data isFalse for all of the FMTSICs, (2) determine first supplemental touchinputs and optionally determine supplemental haptic feedback commands if“PMUT Triggered” Boolean data is True for at least one of the FMTSICs(Touched FMTSICs) and light-force conditions are satisfied for all ofthe Touched FMTSICs, and (3) determine primary touch inputs andoptionally determine primary haptic feedback commands if “PMUTTriggered” Boolean data is True for at least one of the FMTSICs (TouchedFMTSICs) and light-force conditions are not satisfied for at least oneof the Touched FMTSICs. The processor is configured to determinecombined inputs in accordance with (1) primary inputs from the otherinput sub-system and (2) the zeroth supplemental touch inputs or thefirst supplemental touch inputs.

In yet another aspect, a method includes: (1) configuring a touch-inputsub-system including a cover layer and a plurality of FMTSICs coupled tothe inner surface of the cover layer at respective positions, (2)configuring a haptic transducer, (3) configuring a haptic controller todrive the haptic transducer, (4) transmitting, by the PMUT transmittersof each of the FMTSICs, ultrasound signals towards the cover layer, (5)outputting, from the PMUT receivers of each of the FMTSICs, voltagesignals (PMUT voltage signals) in response to reflected ultrasoundsignals arriving from the cover layer, (6) converting, by the signalprocessing circuitry of each of the FMTSICs, the respective PMUT voltagesignals to PMUT digital data, (7) outputting, from the PMFEs of each ofthe FMTSICs, voltage signals (PMFE voltage signals) in accordance with atime-varying strain at respective portions of a piezoelectric layer atthe respective PMFEs resulting from a low-frequency mechanicaldeformation, and (8) converting, by the signal processing circuitry ofeach of the FMTSICs, the respective PMFE voltage signals to PMFE digitaldata.

In yet another aspect, the method is a method of delineating a locationof a virtual button by haptic feedback. The method additionallyincludes: (A9) determining, by the touch-input sub-system, supplementalhaptic feedback commands if “PMUT Triggered” Boolean data is True for atleast one of the FMTSICs (Touched FMTSICs) and light-force conditionsare satisfied for all of the Touched FMTSICs, (A10) determining, by thetouch-input sub-system, primary touch inputs if “PMUT Triggered” Booleandata is True for at least one of the FMTSICs (Touched FMTSICs) andlight-force conditions are not satisfied for at least one of the TouchedFMTSICs, and (A11) driving the haptic transducer to generate hapticfeedback in accordance with the supplemental haptic feedback commands.The light-force conditions of each of the FMTSICs include: the PMFEdigital data of the respective FMTSIC indicates an applied force lessthan F_(light). The “PMUT Triggered” Boolean data are obtained from thePMUT digital data.

In yet another aspect, the method is a method of delineating a locationof a virtual button by haptic feedback. The method additionallyincludes: (B2) configuring a processor coupled to the touch-inputsub-system, (B10) determining, by the touch-input sub-system or theprocessor, supplemental haptic feedback commands if “PMUT Triggered”Boolean data is True for at least one of the FMTSICs (Touched FMTSICs)and light-force conditions are satisfied for all of the Touched FMTSICs,(B11) determining, by the touch-input sub-system or the processor,primary touch inputs if “PMUT Triggered” Boolean data is True for atleast one of the FMTSICs (Touched FMTSICs) and light-force conditionsare not satisfied for at least one of the Touched FMTSICs, and (B12)driving the haptic transducer to generate haptic feedback in accordancewith the supplemental haptic feedback commands. The light-forceconditions of each of the FMTSICs include: the PMFE digital data of therespective FMTSIC indicates an applied force less than F_(light). The“PMUT Triggered” Boolean data are obtained from the PMUT digital data.

In yet another aspect, the method is a method of determining user-input.The method additionally includes: (C2) configuring another inputsub-system, (C3) configuring a processor coupled to the touch-inputsub-system and to the other input sub-system, (C11) determining, by thetouch-input sub-system or the processor, zeroth supplemental touchinputs if “PMUT Triggered” Boolean data is False for all of the FMTSICs,(C12) determining, by the touch-input sub-system or the processor, firstsupplemental touch inputs and supplemental haptic feedback commands if“PMUT Triggered” Boolean data is True for at least one of the FMTSICs(Touched FMTSICs) and light-force conditions are satisfied for all ofthe Touched FMTSIC, (C13) determining, by the touch-input sub-system orprocessor, primary touch inputs if “PMUT Triggered” Boolean data is Truefor at least one of the FMTSICs (Touched FMTSICs) and light-forceconditions are not satisfied for at least one of the Touched FMTSICs,and (C14) determining, by the processor, combined inputs in accordancewith (1) primary inputs from the other input sub-system and (2) thezeroth supplemental touch inputs or the first supplemental touch inputs.The light-force conditions of each of the FMTSICs include: the PMFEdigital data of the respective FMTSIC indicates an applied force lessthan F_(light). The “PMUT Triggered” Boolean data are obtained from thePMUT digital data.

The above summary of the present invention is not intended to describeeach disclosed embodiment or every implementation of the presentinvention. The description that follows more particularly exemplifiesillustrative embodiments. In several places throughout the application,guidance is provided through examples, which examples can be used invarious combinations. In each instance of a list, the recited listserves only as a representative group and should not be interpreted asan exclusive list.

BRIEF DESCRIPTION OF THE FIGURES

The disclosure may be more completely understood in consideration of thefollowing detailed description of various embodiments of the disclosurein connection with the accompanying drawings, in which:

FIG. 1 is a schematic view of a system including two force-measuring andtouch-sensing integrated circuits (FMTSICs).

FIG. 2 is a schematic cross-sectional view of a force-measuring andtouch-sensing integrated circuit.

FIG. 3 is a schematic cross-sectional view of a certain portion of theforce-measuring and touch-sensing integrated circuit of FIG. 2.

FIGS. 4, 5, and 6 are schematic cross-sectional views of a PMUTtransmitter.

FIGS. 7, 8, and 9 are schematic cross-sectional views of a PMUTreceiver.

FIG. 10 is a schematic cross-sectional view of a piezoelectricmicromechanical force-measuring element (PMFE).

FIGS. 11, 12, and 13 are schematic side views of force-measuring andtouch-sensing integrated circuits and a cover layer, attached to eachother and undergoing deformation.

FIG. 14 is a schematic top view of a MEMS portion of a force-measuringtouch-sensing integrated circuit.

FIG. 15 is a flow diagram of a process of making a force-measuring andtouch-sensing integrated circuit and a user-input system.

FIG. 16 is an electronics block diagram of a force-measuring andtouch-sensing integrated circuit.

FIG. 17 is a diagram showing a graphical plot of example PMUT digitaldata over a longer time duration.

FIG. 18 is a diagram showing graphical plots of example PMUT digitaldata over a shorter time duration.

FIGS. 19 and 20 are diagrams showing graphical plots of PMUT digitaldata and PMFE digital data, respectively, in response to an exampletouch event.

FIG. 21 is a block diagram of a force-measuring and touch-sensingintegrated circuit.

FIGS. 22, 23, and 24 are schematic views of an illustrative smartphone.

FIGS. 25 and 26 are schematic views of elements of touch-input systems.

FIGS. 27, 28, 29, and 30 are schematic diagrams of implementations ofuser-input systems.

FIG. 31 is a flow diagram of a method of delineating a location of avirtual button by haptic feedback.

FIG. 32 is a flow diagram of a method of determining user-input.

DETAILED DESCRIPTION OF ILLUSTRATIVE EMBODIMENTS

The present disclosure relates to user-input systems and methods ofdelineating a location of a virtual button by haptic feedback and ofdetermining user-input.

In this disclosure:

The words “preferred” and “preferably” refer to embodiments of theinvention that may afford certain benefits, under certain circumstances.However, other embodiments may also be preferred, under the same orother circumstances. Furthermore, the recitation of one or morepreferred embodiments does not imply that other embodiments are notuseful and is not intended to exclude other embodiments from the scopeof the invention.

The terms “comprises” and variations thereof do not have a limitingmeaning where these terms appear in the description and claims.

Unless otherwise specified, “a,” “an,” “the,” and “at least one” areused interchangeably and mean one or more than one.

The recitations of numerical ranges by endpoints include all numberssubsumed within that range (e.g., 1 to 5 includes 1, 1.5, 2, 2.75, 3,3.80, 4, 5, etc.).

For any method disclosed herein that includes discrete steps, the stepsmay be conducted in any feasible order. As appropriate, any combinationof two or more steps may be conducted simultaneously.

FIG. 1 is a schematic view of an input system 100. In the example shown,system 100 includes force-measuring and touch-sensing integratedcircuits (FMTSICs) 102, 106. Each of the FMTSICs 102, 106 has anelectrical interconnection surface (bottom surface) 101, 105 and anultrasound transmission surface (top surface) 103, 107. In the exampleshown, each FMTSIC 102, 106 is in the form of a semiconductor die in apackage. The FMTSICs are mounted to a flexible circuit substrate(flexible circuit) 108 (e.g., an FPC or flexible printed circuit) on theelectrical interconnection surfaces 101, 105. The flexible circuit 108is electrically and mechanically connected to a printed circuit board(PCB) 112 via a connector 116. Other ICs 114 are mounted on the PCB 112,and such other ICs 114 could be a microcontroller (MCU), microprocessor(MPU), and/or a digital signal processor (DSP), for example. These otherICs 114 could be used to run programs and algorithms to analyze andcategorize touch events based on data received from the FMTSICs 102,106. Other ICs 114 can also be mounted to the flexible circuit.

System 100 includes a cover layer 120 having an exposed outer surface124 and an inner surface 122. The cover layer 120 could be of any robustlayer(s) that transmits ultrasound waves, such as wood, glass, metal,plastic, leather, fabric, and ceramic. The cover layer should be robustbut should be sufficiently deformable, such that a deformation of thecover layer is transmitted to the PMFEs in the FMTSICs, as described inFIGS. 12, 13, and 14. The cover layer 120 could also be a compositestack and could be a composite stack of any of the foregoing materials.The FMTSICs 102, 106 are adhered to or attached to the inner surface 122of the cover layer 120 by a layer of adhesive 110. The choice ofadhesive 110 is not particularly limited as long as the FMTSIC remainsattached to the cover layer. The adhesive 110 could be double-sidedtape, pressure sensitive adhesive (PSA), epoxy adhesive, or acrylicadhesive, for example. FMTSICs 102, 106 are coupled to the inner surface122. In operation, the FMTSICs 102, 106 generate ultrasound waves inlongitudinal modes that propagate along a normal direction 190, shown inFIG. 1 as being approximately normal to the exposed outer surface 124and the inner surface 122 of the cover layer. Stated more precisely, thenormal direction 190 is normal to a piezoelectric layer. Since thepiezoelectric layer defines a plane of a piezoelectric capacitor, thenormal direction 190 is approximately normal to a plane of thepiezoelectric capacitor. The generated ultrasound waves exit the FMTSICs102, 106 and travel through the respective ultrasound transmissionsurfaces 103, 107, through the adhesive layer 110, then through theinner surface 122, and then through the cover layer 120. The ultrasoundwaves reach a sense region 126 of the exposed outer surface 124. Thesense region 126 is a region of the exposed outer surface 124 thatoverlaps the FMTSICs 102, 106.

FIG. 1 illustrates a use case in which a human finger 118 is touchingthe cover layer at the sense region 126. If there is no object touchingthe sense region 126, the ultrasound waves that have propagated throughthe cover layer 120 are reflected at the exposed outer surface (at theair-material interface) and the remaining echo ultrasound waves travelback toward the FMTSICs 102, 106. On the other hand, if there is afinger 118 touching the sense region, there is relatively largeattenuation of the ultrasound waves by absorption through the finger. Asa result, it is possible to detect a touch event by measuring therelative intensity or energy of the echo ultrasound waves that reach theFMTSICs 102, 106.

It is possible to distinguish between a finger touching the sense region126 and a water droplet landing on the sense region 126, for example.When a finger touches the sense region 126, the finger would also exerta force on the cover layer 120. The force exerted by the finger on thecover layer can be detected and measured using the PMFEs in the FMTSIC.On the other hand, when a water droplet lands on the sense region, theforce exerted by the water droplet on the PMFEs would be quite small,and likely less than a noise threshold. More generally, it is possibleto distinguish between a digit that touches and presses the sense region126 and an inanimate object that comes into contact with the senseregion 126. In both cases (finger touching the sense region or waterdroplet landing on the sense region), there would be a noticeabledecrease in an amplitude of the PMUT receiver signal, indicating a touchat the sense region, but there might not be enough information from thePMUT receiver signal to distinguish between a finger and a waterdroplet.

FIG. 1 shows a finger-touch zone 119, which is a zone of contact betweenthe finger 118 and the cover layer 120. Finger-touch zone 119 has a size(a lateral dimension) that depends on factors such as size of the finger118 and whether the finger is a bare finger or a glove-covered finger.Typically, a finger-touch zone 119 can have a size in a range of 3 mm to7 mm. In the example shown, FMTSICs 102 and 106 are separated from eachother by a distance smaller than the finger-touch zone 119. Accordingly,FMTSICs 102 and 106 can correspond to a single virtual button. Atouch-input system can have multiple virtual buttons, and the virtualbuttons can be separated from each other by a distance greater than afinger-touch zone.

System 100 can be implemented in numerous apparatuses. For example, theFMTSICs can replace conventional buttons on Smartphones, keys oncomputer keyboards, sliders, or track pads. The interior contents 128 ofan apparatus (e.g., FMTSICs 102, 106, flexible circuit 108, connector116, PCB 112, other ICs 114) can be sealed off from the exterior 123 ofthe cover layer 120, so that liquids on the exterior 123 cannotpenetrate into the interior 121 of the apparatus. The ability to sealthe interior of an apparatus from the outside helps to make theapparatus, such as a Smartphone or laptop computer, waterproof. Thereare some applications, such as medical applications, where waterproofbuttons and keyboards are strongly desired. The apparatus can be amobile appliance (e.g., Smartphone, tablet computer, laptop computer), ahousehold appliance (e.g., washing machine, dryer, light switches, airconditioner, refrigerator, oven, remote controller devices), a medicalappliance, an industrial appliance, an office appliance, an automobile,or an airplane, for example.

The force-measuring, touch-sensing integrated circuit (FMTSIC) is shownin greater detail in FIG. 2. FIG. 2 is a cross-sectional view the FMTSIC20, which is analogous to FMTSIC 102, 106 in FIG. 1. FMTSIC 20 is shownencased in a package 22, with an ultrasound transmission surface (topsurface) 26 and electrical interconnection surface (bottom surface) 24.Ultrasound transmission surface 26 is analogous to surfaces 103, 107 inFIG. 1 and electrical interconnection surface 24 is analogous tosurfaces 101, 105 in FIG. 1. The FMTSIC 20 includes a package substrate30, semiconductor portion (chip) 28 mounted to the package substrate 30,and an encapsulating adhesive 32, such as an epoxy adhesive. After thesemiconductor die 28 is mounted to the package substrate 30, wire bondconnections 38 are formed between the die 28 and the package substrate30. Then the entire assembly including the die 28 and the packagesubstrate 30 are molded (encapsulated) in an epoxy adhesive 32. Theepoxy side (top surface or ultrasound transmission surface 26) of theFMTSIC is adhered to (coupled to) the inner surface 122 of the coverlayer 120. The FMTSIC 20 is shown mounted to the flexible circuit 108.It is preferable that the FMTSIC have lateral dimensions no greater than10 mm by 10 mm. The wire bond connection is formed between the topsurface 36 of the semiconductor die 28 and the package substrate 30.Alternatively, electrical interconnections can be formed between thebottom surface 34 of the semiconductor die 28 and the package substrate.The semiconductor die 28 consists of an application-specific integratedcircuit (ASIC) portion and a micro-electro-mechanical systems (MEMS)portion. A selected portion 130 of the semiconductor die 28 is shown incross-section in FIG. 3.

FIG. 3 is a schematic cross-sectional view of a portion 130 of theforce-measuring and touch-sensing integrated circuit of FIG. 2. Thesemiconductor die 28 includes a MEMS portion 134 and an ASIC portion136. Between the ASIC portion 136 and the MEMS portion 134, the MEMSportion 134 is closer to the ultrasound transmission surface 26 and theASIC portion 136 is closer to the electrical interconnection surface 24.The ASIC portion 136 consists of a semiconductor substrate 150 andsignal processing circuitry 137 thereon. Typically, the semiconductorsubstrate is a silicon substrate, but other semiconductor substratessuch as silicon-on-insulator (SOI) substrates can also be used.

The MEMS portion 134 includes a PMUT transmitter 142, a PMUT receiver144, and a PMFE 146. The MEMS portion 134 includes a thin-filmpiezoelectric stack 162 overlying the semiconductor substrate 150. Thethin-film piezoelectric stack 162 includes a piezoelectric layer 160,which is a layer exhibiting the piezoelectric effect. Suitable materialsfor the piezoelectric layer 160 are aluminum nitride, scandium-dopedaluminum nitride, polyvinylidene fluoride (PVDF), lead zirconatetitanate (PZT), K_(x)Na_(1-x)NbO₃ (KNN), quartz, zinc oxide, and lithiumniobate, for example. For example, the piezoelectric layer is a layer ofaluminum nitride having a thickness of approximately 1 μm. Thepiezoelectric layer 160 has a top major surface 166 and a bottom majorsurface 164 opposite the top major surface 166. In the example shown,the thin-film piezoelectric stack 162 additionally includes a topmechanical layer 156, attached to or adjacent to (coupled to) top majorsurface 166, and a bottom mechanical layer 154, attached to or adjacentto (coupled to) bottom major surface 164. In the example shown, thethickness of the top mechanical layer 156 is greater than the thicknessof the bottom mechanical layer 154. In other examples, the thickness ofthe top mechanical layer 156 can be smaller than the thickness of thebottom mechanical layer 154. Suitable materials for the mechanicallayer(s) are silicon, silicon oxide, silicon nitride, and aluminumnitride, for example. Suitable materials for the mechanical layer(s) canalso be a material that is included in the piezoelectric layer 160,which in this case is aluminum nitride. In the example shown, the topmechanical layer and the bottom mechanical layer contain the samematerial. In other examples, the top mechanical layer and the bottommechanical layer are of different materials. In other examples, one ofthe top mechanical layer and the bottom mechanical layer can be omitted.When coupled to the cover layer, the FMTSIC 20 is preferably orientedsuch that the piezoelectric layer 160 faces toward the cover layer 120.For example, the FMTSIC 20 is oriented such that the piezoelectric layer160 and the cover layer 120 are approximately parallel.

For ease of discussion, only one of each of the PMUT transmitters, PMUTreceivers, and PMFEs is shown in FIG. 3. However, a typical FMTSIC cancontain a plurality of PMUT transmitters, PMUT receivers, and PMFEs. ThePMUT transmitters, the PMUT receivers, and the PMFEs are located alongrespective lateral positions along the thin-film piezoelectric stack162. Each PMUT transmitter, PMUT receiver, and PMFE includes arespective portion of the thin-film piezoelectric stack.

Each of the PMUTs is configured as a transmitter (142) or a receiver(144). Each PMUT (142, 144) includes a cavity (192, 194) and arespective portion of the thin-film piezoelectric stack 162 overlyingthe cavity (192, 194). The cavities are laterally bounded by an anchorlayer 152 which supports the thin-film piezoelectric stack. Suitablematerials for the anchor layer 152 are silicon, silicon nitride, andsilicon oxide, for example. Suitable materials for the anchor layer 152can also be a material that is included in the piezoelectric layer 160,which in this case is aluminum nitride. Each PMUT (142, 144) includes afirst PMUT electrode (172, 174) positioned on a first side (bottomsurface) 164 of the piezoelectric layer 160 and a second PMUT electrode(182, 184) positioned on a second side (top surface) 166 opposite thefirst side. In each PMUT (142, 144), the first PMUT electrode (172,174), the second PMUT electrode (182, 184), and the piezoelectric layer160 between them constitute a piezoelectric capacitor. The first PMUTelectrodes (172, 174) and the second PMUT electrodes (182, 184) arecoupled to the signal processing circuitry 137. The cavities (172, 174)are positioned between the thin-film piezoelectric stack 162 and thesemiconductor substrate 150. In the example shown, the FMTSIC 20 is inthe form of an encapsulated package 22. The cavities 192, 194 arepreferably under low pressure (pressure lower than atmospheric pressureor in vacuum) and remain so because of the package 22.

Each PMFE 146 includes a respective portion of the thin-filmpiezoelectric stack 162. Each PMFE 146 includes a first PMFE electrode176 positioned on a first side (bottom surface) 164 of the piezoelectriclayer 160 and a second PMFE electrode 186 positioned on a second side(top surface) 166 opposite the first side. In each PMFE 146, the firstPMFE electrode 176, the second PMFE electrode 186, and the piezoelectriclayer 160 between them constitute a piezoelectric capacitor. The PMFEsare coupled to the signal processing circuitry 137. In the exampleshown, the PMFE is not overlying any cavity.

The PMUT transmitter 142 is shown in cross section in FIG. 4. In theexample shown, the thickness of the top mechanical layer 156 is greaterthan the thickness of the bottom mechanical layer 154, and the topmechanical layer 156 and the bottom mechanical layer contain the samematerial, aluminum nitride. In this case, the neutral axis 158 ispositioned within the top mechanical layer 156. The neutral axis is theaxis in the beam (in this case, the beam is the piezoelectric stack 162)along which there are no normal stresses or strains during bending. FIG.4 shows the PMUT transmitter in a quiescent state, in which there is novoltage applied between the first PMUT electrode 172 and the second PMUTelectrode 182. The piezoelectric layer 160 has a built-in polarization(piezoelectric polarization) that is approximately parallel to normaldirection 190. Normal direction 190 is normal to the piezoelectric layer160. Normal direction 190 is approximately normal to a plane of therespective piezoelectric capacitor. FIG. 5 shows the PMUT transmitter ina first transmitter state, in which there is a first transmitter voltageV_(Tx1) (corresponding to a certain polarity and magnitude) appliedbetween the electrodes (172, 182). As a result, the portion of thepiezoelectric stack 162 overlying the cavity 192 flexes upward (awayfrom the cavity 192). In a middle region in between the inflectionpoints of the piezoelectric stack, there is compressive (negative)strain in portions of the piezoelectric stack 162 below the neutral axis158, including the piezoelectric layer 160, and tensile (positive)strain in portions of the piezoelectric stack 162 above the neutral axis158.

FIG. 6 shows the PMUT transmitter in a second transmitter state, inwhich there is a second transmitter voltage V_(Tx2) (corresponding to acertain polarity and magnitude) applied between the PMUT electrodes(172, 182). In a middle region in between the inflection points of thepiezoelectric stack, there is tensile (positive) strain in portions ofthe piezoelectric stack 162 below the neutral axis 158, including thepiezoelectric layer 160, and compressive (negative) strain in portionsof the piezoelectric stack 162 above the neutral axis 158. As a result,the portion of the piezoelectric stack 162 overlying the cavity 192flexes downward (toward the cavity 192). The signal processing circuitry137 is operated to generate and apply a time-varying voltage signalV_(Tx)(t) between the PMUT electrodes (172, 182) of the PMUT transmitter142. If the time-varying voltage signal oscillates between the firsttransmitter voltage and the second transmitter voltage at a certainfrequency, the portion of the piezoelectric stack 162 oscillates betweenthe first transmitter state and the second transmitter state at thatfrequency. As a result, the PMUT transmitter generates (transmits), uponapplication of the time-varying voltage signal, ultrasound signalspropagating along the normal direction 190. Because of the presence ofthe cavity 192 at a low pressure, a relatively small fraction of thegenerated ultrasound energy is transmitted downward toward the cavity192, and a relatively large fraction of the generated ultrasound energyis transmitted upward away from the cavity 192. The PMUT transmittersare configured to transmit ultrasound signals of a frequency in a rangeof 0.1 MHz to 25 MHz.

The PMUT receiver 144 is shown in cross section in FIGS. 7. FIG. 7 showsthe PMUT receiver in a quiescent state, in which there is no flexing ofthe piezoelectric stack 162 away from or towards the cavity 194. In thequiescent state, there is no voltage generated between the PMUTelectrodes (174, 184). FIG. 8 shows the PMUT receiver in a firstreceiver state, in which a positive ultrasound pressure wave is incidenton the PMUT receiver, along the normal direction 190, to cause theportion of the piezoelectric stack 162 overlying the cavity 194 to flexdownwards (towards the cavity 194). In a middle region in between theinflection points of the piezoelectric stack, there is tensile(positive) strain in portions of the piezoelectric stack 162 below theneutral axis 158, including the piezoelectric layer 160, and compressive(negative) strain in portions of the piezoelectric stack 162 above theneutral axis 158. As a result, a first receiver voltage V_(Rx1)(corresponding to a certain polarity and magnitude) is generated betweenthe PMUT electrodes (174, 184).

FIG. 9 shows the PMUT receiver in a second receiver state, in which anegative ultrasound pressure wave is incident on the PMUT receiver,along the normal direction 190, to cause the portion of thepiezoelectric stack 162 overlying the cavity 194 to flex upwards (awayfrom the cavity 194). In a middle region in between the inflectionpoints of the piezoelectric stack, there is compressive (negative)strain in portions of the piezoelectric stack 162 below the neutral axis158, including the piezoelectric layer 160, and tensile (positive)strain in portions of the piezoelectric stack 162 above the neutral axis158. As a result, a second receiver voltage V_(Rx2) (corresponding to acertain polarity and magnitude) is generated between the PMUT electrodes(174, 184). If ultrasound signals are incident on the PMUT receiver 144along the normal direction 190 causing the portion of the piezoelectricstack 162 to oscillate between the first receiver state and the secondreceiver state, a time-varying voltage signal V_(Rx)(t) oscillatingbetween the first receiver voltage and the second receiver voltage isgenerated between the PMUT electrodes (174, 184). The time-varyingvoltage signal is amplified and processed by the signal processingcircuitry 137.

In operation, the PMUT transmitter 142 is configured to transmit, uponapplication of voltage signals between the PMUT transmitter electrodes(172, 182), ultrasound signals of a first frequency F₁, in longitudinalmode(s) propagating along a normal direction 190 approximately normal tothe piezoelectric layer 160 away from the cavity 192 towards the senseregion 126. The ultrasound signals propagate towards the sense region126 of the cover layer 120 to which FMTSIC 20 is coupled. Uponapplication of the voltage signals, the respective portion of thepiezoelectric stack overlying the cavity 192 (of the PMUT transmitter142) oscillates with a first frequency F₁ between a first transmitterstate and a second transmitter state to generate ultrasound signals ofthe first frequency F₁. The PMUT receiver 144 is configured to output,in response to ultrasound signals of the first frequency F₁ arrivingalong the normal direction, voltage signals between the PMUT receiverelectrodes (174, 184). In response to ultrasound signals of the firstfrequency F₁ arriving along the normal direction, the portion of thethin-film piezoelectric stack 162 overlying the cavity oscillates at thefirst frequency F₁. Some fraction of the ultrasound signals transmittedby the PMUT transmitter 142 returns to the PMUT receiver 144 as an echoultrasound signal. In the use case illustrated in FIG. 1, the relativeamplitude or energy of the echo ultrasound signal depends upon thepresence of a digit (e.g., human finger) or other object (e.g., waterdroplet) touching the sense region 126. If the sense region 126 istouched by a digit or other object, there is greater attenuation of theecho ultrasound signal than if there is no touching at the sense region126. By amplifying and processing the time-varying voltage signal fromthe PMUT receiver at the signal processing circuitry, these touch eventscan be detected.

A portion 130 of the FMTSIC 20 containing a PMFE 146 is shown in crosssection in FIG. 10. Also shown is the ASIC portion 136 that is under thePMFE 146 and the encapsulating adhesive 32 that is above the PMFE 146.FIG. 10 shows the PMFE in a quiescent state, in which there is noflexing of the piezoelectric stack 162. In the quiescent state, there isno voltage generated between the PMFE electrodes (176, 186).

FIGS. 11, 12, and 13 are schematic side views of an FMTSIC 20 and acover layer 120 attached to or adhered to (coupled to) each other. A topsurface (ultrasound transmission surface) 26 of FMTSIC 20 is coupled toinner surface 122 of the cover layer 120. FMTSIC 20 and cover layer 120overlie a rigid substrate 135. For ease of viewing, other components ofsystem 100 (e.g., flexible circuit 108, ICs 114) have been omitted.FMTSIC 20 includes PMFEs 146. In the examples shown, two anchor posts131, 133 fix the two ends of the cover layer 120 to the substrate 135.

In the example of FIG. 11, FMTSIC 20 is not anchored to the rigidsubstrate 135 and can move with the cover layer 120 when the cover layer120 is deflected upwards or downwards. A downward force 117, shown as adownward arrow, is applied by a finger (or another object) pressingagainst the outer surface 124 of the cover layer 120 at the sense region126 for example. A finger pressing against or tapping the outer surface124 are examples of touch excitation, or more generally, excitation. Inthe example shown in FIG. 11, the cover layer 120 is deflected in afirst direction (e.g., downwards) in response to a touch excitation atthe sense region 126. FMTSIC 20 is located approximately half-waybetween the anchor posts 131, 133 and sense region 126 overlaps FMTSIC20. A neutral axis 125 is located within the cover layer 120. A lowerportion 127 of the cover layer 120, below the neutral axis 125, is undertensile (positive) strain at the sense region 126, represented byoutward pointing arrows, primarily along lateral direction 191,perpendicular to the normal direction 190. The lateral direction 191 isapproximately parallel to the piezoelectric layer 160 at the respectivelocation of the piezoelectric layer 160 (at region 126). An upperportion 129 of the cover layer 120, above the neutral axis 125, is undercompressive (negative) strain at the sense region 126, represented byinward pointing arrows, primarily along lateral direction 191. SinceFMTSIC 20 is coupled to the inner surface 122, adjacent to the lowerportion 127, the PMFEs 146 are also under tensile (positive) strain.Typically, the entire FMTSIC 20 may be deflected under the applieddownward force 117. In the example shown in FIG. 11, the PMFEs 146 areunder a positive strain, and the respective portions of thepiezoelectric layer 160 at the PMFEs 146 undergo expansion along alateral direction 191. As a result, an electrical charge is generated ateach PMFE (146) between the respective PMFE electrodes (176, 186). Thiselectrical charge is detectable as a first deflection voltage V_(d1)(corresponding to strain of a certain polarity and magnitude). Thepolarity of the first deflection voltage V_(d1) at a PMFE depends uponthe polarity of the strain (positive strain (tensile) or negative strain(compressive)) at the respective portion of the piezoelectric layerbetween the respective PMFE electrodes of the PMFE. The magnitude of thefirst deflection voltage V_(d1) at a PMFE depends upon the magnitude ofthe strain at the respective portion of the piezoelectric layer betweenthe respective PMFE electrodes of the PMFE. Subsequently, when thedownward force 117 is no longer applied to the sense region 126, thecover layer 120 deflects in a second direction opposite the firstdirection (e.g., upwards). This is detectable as a second deflectionvoltage V_(d2) (corresponding to strain of a certain polarity andmagnitude). The polarity of the second deflection voltage V_(d2) at aPMFE depends upon the polarity of the strain at the respective portionof the piezoelectric layer between the respective PMFE electrodes of thePMFE. The magnitude of the second deflection voltage V_(d2) at a PMFEdepends upon the magnitude of the strain at the respective portion ofthe piezoelectric layer between the respective PMFE electrodes of thePMFE.

FIG. 11 shows a second FMTSIC 20A, including PMFEs 146A. A top surface(ultrasound transmission surface) 26A of FMTSIC 20A is coupled to innersurface 122 of the cover layer 120. FMTSIC 20A overlies the rigidsubstrate 135 and is located at a second region 126A, between anchorpost 131 and first FMTSIC 20. Note that FMTSIC 20A is laterallydisplaced from the location where the downward force 117 is applied tothe outer surface 124 (at sense region 126). The lower portion 127 ofthe cover layer 120 is under compressive (negative) strain at the secondregion 126A, represented by inward pointing arrows, primarily along thelateral direction 191A, perpendicular to the normal direction 190A. Thelateral direction 191A is approximately parallel to the piezoelectriclayer 160 at the respective location of the piezoelectric layer 160 (atsecond region 126A). The upper portion 129 of the cover layer 120 isunder tensile (positive) strain at the second region 126A, representedby outward pointing arrows, primarily along the lateral direction 191A.Since FMTSIC 20A is coupled to the inner surface 122, adjacent to thelower portion 127, the PMFEs 146A are also under compressive (negative)strain. These examples illustrate that when the cover layer and theFMTSICs undergo deflection in response to a touch excitation at theouter surface, expansion and/or compression of the piezoelectric layeralong the lateral direction may be induced by the deflection of thecover layer.

In the example shown in FIG. 12, the bottom surface 24 of FMTSIC 20 isanchored to the rigid substrate 135. When downward force 117 is appliedto the outer surface 124 of the cover layer 120 at sense region 126, theportion of the cover layer 120 at the sense region 126 transmits thedownward force along normal direction 190. The portion of the coverlayer 120 at the sense region 126 and the FMTSIC 20 undergo compressionalong normal direction 190. Consequently, the PMFEs 146 includingpiezoelectric layer 160 are compressed along the normal direction 190,approximately normal to the piezoelectric layer 160. As a result, anelectrical charge is generated between the PMFE electrodes (176, 186).This electrical charge is detectable as a voltage V_(c) (correspondingto a strain of a certain polarity and magnitude) between the PMFEelectrodes. The downward force 117 that causes this compression isapplied during a touch excitation, such as tapping at or pressingagainst the outer surface 124. The pressing or the tapping can berepetitive. Typically, the entire FMTSIC 20 may undergo compression.Subsequently, the piezoelectric layer 160 relaxes from the compressedstate. In other cases, there may also be compression along a lateraldirection 191, or along other directions.

In the example shown in FIG. 13, FMTSIC 20 is not anchored to the rigidsubstrate 135. A downward force 139, shown as a downward arrow, isapplied to the outer surface 124 of the cover layer 120 at the senseregion 126. The downward force 139 is generated as a result of an impactof touch excitation at the sense region 126. For example, the downwardforce 139 is generated as a result of the impact of a finger (or anotherobject) tapping the outer surface at the sense region 126. The touchexcitation (e.g., tapping) can be repetitive. The impact of the touchexcitation (e.g., tapping) generates elastic waves that travel outwardfrom the location of the impact (on the outer surface 124 at senseregion 126) and at least some of the elastic waves travel toward theinner surface 122. Accordingly, at least some portion 149 of the elasticwaves are incident on the FMTSIC 20.

In general, an impact of a touch excitation (e.g., tapping) on a surfaceof a stack (e.g., cover layer) can generate different types of wavesincluding pressure waves, shear waves, surface waves and Lamb waves.Pressure waves, shear waves, and surface waves are in a class of wavescalled elastic waves. Pressure waves (also called primary waves orP-waves) are waves in which the molecular oscillations (particleoscillations) are parallel to the direction of propagation of the waves.Shear waves (also called secondary waves or S-waves) are waves in whichthe molecular oscillations (particle oscillations) are perpendicular tothe direction of propagation of the waves. Pressure waves and shearwaves travel radially outwards from the location of impact. Surfacewaves are waves in which the energy of the waves are trapped within ashort depth from the surface and the waves propagate along the surfaceof the stack. Lamb waves are elastic waves that can propagate in plates.When an object (e.g., a finger) impacts a surface of a stack, differenttypes of elastic waves can be generated depending upon the specifics ofthe impact (e.g., speed, angle, duration of contact, details of thecontact surface), the relevant material properties (e.g., materialproperties of the object and the stack), and boundary conditions. Forexample, pressure waves can be generated when an impact of a touchexcitation at the outer surface is approximately normal to the outersurface. For example, shear waves can be generated when an impact of atouch excitation at the outer surface has a component parallel to theouter surface, such as a finger hitting the outer surface at an obliqueangle or a finger rubbing against the outer surface. Some of theseelastic waves can propagate towards the FMTSIC 20 and PMFEs 146. If thestack is sufficiently thin, then some portion of surface waves canpropagate towards the FMTSIC 20 and PMFEs 146 and be detected by thePMFEs 146.

Accordingly, when elastic waves 149 are incident on the FMTSIC 20 andPMFEs 146, the elastic waves induce time-dependent oscillatorydeformation to the piezoelectric layer 160 at the PMFE 146. Thisoscillatory deformation can include: lateral deformation (compressionand expansion along the lateral direction 191 approximately parallel topiezoelectric layer 160), normal deformation (compression and expansionalong the normal direction 190 approximately normal to the piezoelectriclayer 160), and shear deformation. As a result, time-varying electricalcharges are generated at each PMFE (146) between the respective PMFEelectrodes (176, 186). These time-varying electrical charges aredetectable as time-varying voltage signals. The signal processingcircuitry amplifies and processes these time-varying voltage signals.Typically, the time-dependent oscillatory deformations induced by animpact of a touch excitation are in a frequency range of 10 Hz to 1 MHz.For example, suppose that elastic waves 149 include pressure wavesincident on the PMFEs 146 along the normal direction 190; these pressurewaves may induce compression (under a positive pressure wave) andexpansion (under a negative pressure wave) of the piezoelectric layer160 along the normal direction 190. As another example, suppose thatelastic waves 149 include shear waves incident on the PMFEs 146 alongthe normal direction 190; these shear waves may induce compression andexpansion of the piezoelectric layer 160 along the lateral direction191.

Consider another case in which a downward force 139A, shown as adownward arrow, is applied to the outer surface 124 at a second region126A, between anchor post 131 and FMTSIC 20. The downward force 139A isgenerated as a result of an impact of touch excitation at the secondregion 126A. The impact of the touch excitation generates elastic wavesthat travel outward from the location of the impact (region 126A) and atleast some of the elastic waves travel towards the inner surface 122.Accordingly, at least some portion 149A of the elastic waves areincident on the FMTSIC 20, causing the piezoelectric layer 160 toundergo time-dependent oscillatory deformation. As a result,time-varying electrical charges are generated at each PMFE (146) betweenthe respective PMFE electrodes (176, 186). These time-varying electricalcharges are detectable as time-varying voltage signals, although theimpact of the touch excitation occurred at a second region 126A that islaterally displaced from the sense region 126.

Elastic waves 149A that reach FMTSIC 20 from region 126A may be weaker(for example, smaller in amplitude) than elastic waves 149 that reachFMTSIC 20 from sense region 126, because of a greater distance betweenthe location of impact and the FMTSIC. An array of PMFEs can beconfigured to be a position-sensitive input device, sensitive to alocation of the impact (e.g., tapping) of a touch excitation. An arrayof PMFEs can be an array of PMFEs in a single FMTSIC or arrays of PMFEsin multiple FMTSICs. For example, a table input apparatus could have anarray of FMTSICs located at respective lateral positions underneath thetable's top surface, in which each FMTSIC would contain at least onePMFE and preferably multiple PMFEs. The signal processing circuitry canbe configured to amplify and process the time-varying voltage signalsfrom the PMFEs and analyze some features of those time-varying voltagesignals. Examples of features of time-varying voltage signals are: (1)amplitudes of the time-varying voltage signals, and (2) the relativetiming of time-varying voltage signals (the “time-of-flight”). Forexample, a PMFE exhibiting a shorter time-of-flight is closer to thelocation of impact than another PMFE exhibiting a longer time-of-flight.The signal processing circuitry can analyze features of time-varyingsignals (e.g., amplitude and/or time-of-flight) from the PMFEs in anarray of PMFEs to estimate a location of impact of a touch excitation.

In operation, PMFE 146 is configured to output voltage signals betweenthe PMFE electrodes (176, 186) in accordance with a time-varying strainat the respective portion of the piezoelectric layer between the PMFEelectrodes (176, 186) resulting from a low-frequency mechanicaldeformation. A touch excitation at the cover layer or at anothercomponent mechanically coupled to the cover layer causes a low-frequencymechanical deformation (of the cover layer or other component at thepoint of excitation). The touch excitation induces effects includingdeflection (as illustrated in FIG. 11), compression (as illustrated inFIG. 12), and/or elastic-wave oscillations (as illustrated in FIG. 13).In an actual touch event, more than one of these effects may beobservable. Consider tapping by a finger as an example of a touchexcitation. As the finger impacts the outer surface 124, elastic wavesare generated which are detectable as time-varying voltage signals atthe PMFEs (FIG. 13). Elastic waves are generated by the impact of thetouch excitation. Subsequently, as the finger presses against the coverlayer, the FMTSIC undergoes deflection (FIG. 11). There is expansion orcompression of the piezoelectric layer along a lateral direction. Thelow-frequency mechanical deformation can be caused by a finger pressingagainst or tapping at outer surface of the cover layer 120, to which theFMTSIC 20 is attached (coupled). The PMFE 146 is coupled to the signalprocessing circuitry 137. By amplifying and processing the voltagesignals from the PMFE at the signal processing circuitry, the strainthat results from the mechanical deformation of the piezoelectric layercan be measured.

It is possible to adjust the relative amplitudes of the PMFE voltagesignals attributable to the elastic-wave oscillations (FIG. 13) andlateral expansion and compression due to deflection (FIG. 11). Forexample, one can choose the cover layer to be more or less deformable.For example, the cover layer 120 of FIG. 13 may be thicker and/or madeof more rigid material than the cover layer 120 of FIG. 11.

PMFE 146 is configured to output voltage signals between the PMFEelectrodes (176, 186) in accordance with a time-varying strain at therespective portion of the piezoelectric layer between the PMFEelectrodes (176, 186) resulting from a low-frequency mechanicaldeformation. Typically, the low-frequency deformation is induced bytouch excitation which is not repetitive (repetition rate is effectively0 Hz) or is repetitive having a repetition rate of 100 Hz or less, or 10Hz or less. These repetition rates correspond to the repetition rates ofa repetitive touch excitation, e.g., a finger repeatedly pressingagainst or tapping the sense region. An example of a repetition ratecalculation is explained with reference to FIG. 20. In the example shownin FIG. 20, the repetition rate is approximately 2.4 Hz.

A touch excitation, or more generally, excitation can occur somewhereother than at the sense region. Consider an implementation of FMTSICs ina portable apparatus, such as a smartphone. In some cases, the coverlayer, to which the FMTSIC is coupled, can be a portion of thesmartphone housing, and in other cases, the housing and the cover layercan be attached to each other, such that forces applied to the housingcan be transmitted to the cover layer. We can refer to both cases as acomponent (e.g., housing) being mechanically coupled to the cover layer.Excitation such as bending of, twisting of, pinching of, typing at, andtapping at the housing can also cause low-frequency mechanicaldeformation. For example, typing at the housing can include typing at atouch panel of the smartphone. There can be a time-varying strain(force) at a respective portion of the piezoelectric layer at a PMFEresulting from this low-frequency deformation.

An FMTSIC can contain multiple PMUT transmitters, PMUT receivers, andPMFEs. FIG. 14 is a top view of a MEMS portion 250 of an FMTSIC. ThePMUTs (PMUT transmitters 204 shown as white circles and PMUT receivers206 shown as grey circles) are arranged in a two-dimensional array,extending along the X-axis (220) and Y-axis (222). The PMUTs arearranged in columns (A, B, C, and D) and rows (1, 2, 3, and 4). In theexample shown, the two-dimensional PMUT array 202 has a square outerperimeter, but in other examples the outer perimeter can have othershapes such as a rectangle. In the example shown, the total number ofPMUTs is 16, of which 12 are PMUT transmitters 204 and 4 are PMUTreceivers 206. In the example shown, the PMUT receivers number less thanthe PMUT transmitters. The PMUTs are shown as circles because theoverlap area of the first (bottom) electrode 172 and the second (top)electrode 174 is approximately circular. In other examples, the overlaparea can have other shapes, such as a square. In the example shown, thePMUTs are of the same lateral size (area), but in other examples PMUTsof different sizes are also possible.

The PMUT transmitters 204 are configured to transmit, upon applicationof voltage signals between the respective first PMUT electrode and therespective second PMUT electrode, ultrasound signals of a firstfrequency F₁, in longitudinal mode(s) propagating along a normaldirection approximately normal to the thin-film piezoelectric stack andaway from the cavities. A benefit to a two-dimensional array of PMUTtransmitters is that by optimization of the voltage signals (timingand/or amplitudes) to each of the PMUT transmitters, the transmittedultrasound signals can be made to interfere constructively to achieve abeam-forming effect if desired. The PMUT receivers 206 are configured tooutput, in response to ultrasound signals of the first frequency F₁arriving along the normal direction, voltage signals between therespective first PMUT electrode and the respective second PMUTelectrode. In the example shown, the piezoelectric capacitorsconstituting the PMUT receivers 206 are connected to each other inparallel. Since the capacitances of these PMUT receivers are addedtogether, this arrangement of PMUT receivers is less sensitive to theeffects of parasitic capacitance.

The MEMS portion includes eight PMFEs (254) arranged in atwo-dimensional array 252. The PMFE array 252 has an opening, which isdevoid of PMFEs, in which the PMUT array 202 is disposed. The PMFEs arearranged into four sets (260, 262, 264, and 266), where each set isassociated with a different X and Y location. Therefore, the PMFE array252 achieves a two-dimensional positional resolution of applied forcesmeasurement. The PMFE array enables calculation of force-resolutionfeatures, discussed hereinbelow. Each PMFE set contains two PMFEs. Inthe example shown, set 260 contains t1 and t2, set 262 contains u1 andu2, set 264 contains v1 and v2, and set 266 contains w1 and w2. ThePMFEs in a set are electrically connected to each other. In thisexample, the piezoelectric capacitors constituting each PMFE in a setare connected to each other in series. An advantage to combining thetouch-sensing (PMUTs) and force-measuring (PMFEs) functions into oneintegrated circuit device is that it becomes possible to distinguishbetween stationary objects that touch but do not apply significant force(e.g., water droplet on sense region 126) and moving objects that touchand apply significant force (e.g., finger).

The PMUT arrays shown in FIGS. 14 illustrated examples of PMUT arraysconfigured to operate at a single frequency F₁, in which the PMUTtransmitters transmit ultrasound signals at F₁ and the PMUT receiversare configured to receive ultrasound signals at frequency F₁. In othercases, PMUT arrays can be configured to operate at frequencies F₁ andF₂. For example, a PMUT array contains first PMUT transmittersconfigured to transmit ultrasound signals at a first frequency F₁, firstPMUT receivers configured to receive ultrasound signals at a firstfrequency second PMUT transmitters configured to transmit ultrasoundsignals at a second frequency F₂, and second PMUT receivers configuredto receive ultrasound signals at a second frequency F₂.

FIG. 15 shows a flow diagram 270 for the process of making a FMTSIC 20and a finger-touch input system. The method includes steps 272, 274,276, and 278. At step 272, the ASIC portion 136 including signalprocessing circuitry 137 is fabricated on a semiconductor substrate(wafer) 150 using a CMOS fabrication process (FIG. 3). At step 274, theMEMS portion 134 is fabricated on top of the ASIC portion 136. At step276, the integrated circuit device, FMTSIC 20, is made. This step 276includes, for example, the singulation of the wafer into dies, themounting of dies onto a package substrate, and the packaging of the dieincluding application of an epoxy adhesive. The making of FMTSICs iscomplete at the end of step 276. Subsequently, a finger-touch inputsystem is made at step 278. This step 278 includes, for example, themounting of one or more FMTSICs and other ICs to a flexible circuitand/or printed circuit board (PCB) and adhering the FMTSICs to aninterior surface of a cover layer of the apparatus.

Step 278 may include a testing procedure carried out on PMFE(s) afteradhering the FMTSIC(s) to the interior surface of the cover layer. Thistesting procedure preferably includes the application of a testingforce, in a range of 0.5 N to 10 N at the sense region. For example,suppose that upon application of a testing force of 7.5 N, a magnitudeof the PMFE digital data (difference between maximum PMFE digital data(e.g., 542 in FIG. 20) and minimum PMFE digital data (e.g., 544 in FIG.20)) is 1280 LSB. It is possible to calculate one or both of thefollowing: (1) a ratio A of a magnitude of the PMFE digital data to aphysical force value; and/or (2) a ratio B of a physical force value toa magnitude of the PMFE digital data. In this example, the ratio A=1280LSB/7.5 N and the ratio B=7.5 N/1280 LSB. These ratios A and B permit aconversion between PMFE digital data (expressed in LSB) and a physicalforce value (applied force value) (expressed in Newtons). Another unitof force is gram-force. These ratios A and/or B can be stored in amemory store (non-volatile memory) of the respective FMTSIC.

Step 278 may include a testing procedure carried out on PMUT(s) afteradhering the FMTSIC(s) to the interior surface of the cover layer. Thistesting procedure preferably includes contacting an object to the senseregion (touch event) in which a force, in a range of 0.5 N to 10 N, isapplied at the sense region. For example, suppose that upon contactingan object in which a testing force of 7.5 N is applied, the PMUT digitaldata decrease by 230 LSB (e.g., from the baseline 426 to a minimumsignal 430 in FIG. 18). Accordingly, the dynamic range (differencebetween baseline and minimum signal) is 230 LSB under application of atesting force of 7.5 N. These dynamic range and testing force data canbe stored in a memory store (non-volatile memory) of the respectiveFMTSIC.

FIG. 16 is an electronics block diagram of the FMTSIC 20, including aMEMS portion 134 and signal processing circuitry 137. The MEMS portionincludes PMUT transmitters 142, PMUT receivers 144, and PMFEs 146.Signal processing circuitry 137 includes a high-voltage domain 280 and alow-voltage domain 290. The high-voltage domain is capable of operatingat higher voltages required for driving the PMUT transmitters. Thehigh-voltage domain includes high-voltage transceiver circuitry 282,including high-voltage drivers. The high-voltage transceiver circuitry282 is connected to the first PMUT electrodes and the second PMUTelectrodes of the PMUT transmitters, via electrical interconnections(wiring) 284. The high-voltage transceiver is configured to outputvoltage pulses of 5 V or greater, depending on the requirements of thePMUT transmitters. The processing circuit blocks 288 are electricallyconnected to the high-voltage transceiver circuitry 282 and theanalog-to-digital converters (ADCs) (296, 306). The processing circuitblocks 288 generate time-varying signals that are transmitted to thehigh-voltage transceiver circuitry 282. The high-voltage transceivercircuitry 282 transmits high-voltage signals to the PMUT transmitters142 in accordance with the time-varying signals from the processingcircuit blocks 288.

The low-voltage domain 290 includes amplifiers (292, 302) andanalog-to-digital converters (ADCs) (296, 306). The processing circuitblocks 288 are also contained in the low-voltage domain 290. Voltagesignals output by the PMUT receivers 144 (represented by gray circles)reach amplifiers 302 via electrical interconnections (wiring) 304 andget amplified by the amplifiers 302. The amplified voltage signals aresent to ADC 306 to be converted to digital signals which can beprocessed or stored by processing circuit blocks 288. Similarly, voltagesignals output by PMFEs 146 reach amplifiers 292 via electricalinterconnections (wiring) 294 and get amplified by the amplifiers 292.These amplified voltage signals are sent to ADC 296 to be converted todigital signals which can be processed or stored by processing circuitblocks 288. The processing circuit blocks 288 could be microcontrollers(MCUs), memories, and digital signal processors (DSPs), for example. Thewiring (284, 294, 304) traverses the semiconductor substrate, whichcontains the signal processing circuitry 137, and the MEMS portion 134,which contains the PMFEs 146, the PMUT transmitters 142, and the PMUTreceivers 144.

In the example shown (FIG. 16), the piezoelectric capacitorsconstituting the PMUT receivers 144 are connected to each other inparallel. Since the capacitances of these PMUT receivers are addedtogether, this arrangement of PMUT receivers is less sensitive to theeffects of parasitic capacitance. Accordingly, there is a unifiedvoltage signal transmitted from the PMUT receivers 144 to the amplifiers302. The piezoelectric capacitors constituting the PMUT transmitters 142are connected in parallel. Accordingly, there is a time-varying signaltransmitted from the high-voltage transceiver circuitry 282 to the PMUTtransmitters 142. The PMFEs 146 are grouped into two sets (p and q onthe left side, r and s on the right side), and the PMFEs in each set areconnected to each other in series. Accordingly, there are two sets ofPMFE signals transmitted from the PMFEs 146 to the amplifiers 292.

An example of a PMUT digital data is shown in FIG. 17, which showsgraphical plot 400 of illustrative PMUT digital data, after ADC andbefore additional processing (e.g., high-pass filtering). The graphicalplot has a horizontal axis 402 showing time t, in which 1 divisioncorresponds to 5000 ms, and a vertical axis 404 showing PMUT digitaldata (e.g., data output from ADC 306 of FIG. 16). Graphical plot 400includes sections 406, 414, 408, 416, 410, 418, and 412 (orderedsequentially). Graphical plot portions 406, 408, 410, and 412 correspondto time periods during which there is nothing touching or coming intocontact with the sense region. These graphical plot sections 406, 408,410, and 412 show the baseline signal, which exhibits a drift. Plotsection 414 corresponds to repetitive pressing of a digit (e.g., afinger) on the sense region, wherein each valley 415 in the PMUT signalcorresponds to one occurrence of the digit pressing at the sense region.In the example shown, plot section 414 shows 10 repetitions of the digitpressing at the sense region. After each repetition, the digit iscompletely released (removed) from the sense region. Plot section 416also corresponds to repetitive pressing of the digit on the senseregion, but after each repetition, the digit is not completely removedfrom the sense region. During the duration of plot section 416, thedigit is in contact with the sense region. Plot section 418 correspondsto the digit touching the sense region and being held against the senseregion continuously.

FIG. 18 shows graphical plots 420, 440, and 470 of illustrative PMUTdigital data. The graphical plots have a horizontal axis 422 showingtime t, in which 1 division corresponds to 200 ms, and a vertical axis424 showing PMUT digital data. Graphical plot 420 is a graphical plot ofPMUT digital data (e.g., data output from ADC 306 of FIG. 16, beforeadditional processing) and corresponds to one occurrence of a digitpressing on the sense region and the digit being completely removed(released) from the sense region. Graphical plot 420 includes plotsections 426, 428, 430, 432, and 434 (ordered sequentially). Graphicalplot portions 426 and 434 correspond to time periods during which thereis nothing touching or coming into contact with the sense region. Thesegraphical plot sections 426 and 434 show the baseline signal. During theduration of plot section 428, the PMUT digital signal is decreasing fromthe baseline (derivative of PMUT digital signal with respect to time isnegative), approximately corresponding to the digit coming into contactwith the sense region and the digit pressing at the sense region. ThePMUT digital signal reaches a minimum at plot section 430. During theduration of plot section 432, the PMUT digital signal is increasing fromthe minimum (derivative of PMUT digital signal with respect to time ispositive), approximately corresponding to the digit being released fromthe sense region.

The PMUT digital signal (420) undergoes additional processing. In theexample shown in FIG. 18, there are two processed outputs (440, 470)from the PMUT digital signal. Plots 440, 470 show the PMUT digitalsignal 420 after passing through a high-pass filter as follows: plot 440shows the high-pass filtered output that is less than or equal to 0 andplot 470 shows the high-pass filtered output that is greater than orequal to 0. The high-pass filter processing can be carried out on theoutput from the ADCs (e.g., ADC 306 of FIG. 16). The high-pass filteringprocess can be carried out at the processing circuit block 288 (FIGS.16, 21).

Graphical plot 440 (negative-side high-pass filtered PMUT digitalsignal) includes plot sections 442, 444, 446, 448, and 450, orderedsequentially. Plot sections 442 and 450 show the baseline signal. Duringthe duration of plot section 444, the high-pass filtered PMUT digitalsignal (negative side) is decreasing from the baseline. The high-passfiltered PMUT digital signal (negative side) reaches a minimum at plotsection 446. During the duration of plot section 448, the high-passfiltered PMUT digital signal (negative side) is increasing from theminimum. Plot sections 444, 446, and 448 can correspond to an object,such as a digit, touching and pressing at the sense region. Accordingly,the negative-side high-pass filtered PMUT digital signal is sometimesreferred to as a press signal.

Graphical plot 470 (positive-side high-pass filtered PMUT digitalsignal) includes plot sections 472, 474, 476, 478, and 480, orderedsequentially. Plot sections 472 and 480 show the baseline signal. Duringthe duration of plot section 474, the high-pass filtered PMUT digitalsignal (positive side) is increasing from the baseline. The high-passfiltered PMUT digital signal (positive side) reaches a maximum at plotsection 476. During the duration of plot section 478, the high-passfiltered PMUT digital signal (positive side) is decreasing from themaximum. Plot sections 474, 476, and 478 can correspond to an object,such as a digit, being released from the sense region. Accordingly, thepositive-side high-pass filtered PMUT digital signal is sometimesreferred to as a release signal or relief signal. An end of the plotsection 448, corresponding to the negative-side high-pass filtered PMUTdigital data increasing toward the baseline, and a beginning of the plotsection 474, corresponding to the positive-side high-pass filtered PMUTdigital data increasing from the baseline, occur approximatelyconcurrently.

A moving time window can be applied to the PMUT digital data beforehigh-pass filtering, shown as plot 420. An illustrative moving timewindow 500, at a particular time, is shown in FIG. 18. Moving timewindow 500 has a predetermined duration 502 and a predetermined dynamicrange 504. In the example shown, the predetermined duration 502 is 200ms. It is preferable that the predetermined duration be in a range of100 ms to 300 ms. In the example shown, the predetermined dynamic range504 corresponds to a difference between a minimum signal (data) 430 andthe baseline signal (data) (426 or 434). It is preferable to set thepredetermined dynamic range to be a dynamic range of the PUT digitaldata (in this example, the PMUT digital data) under application of astandard force in a range of 0.5 N to 10 N at the sense region. The term“standard force” refers to a force that may be exerted during a standardtouch event, such as touching by a finger of a typical person.Preferably, the dynamic range of the PMUT digital data would be knownfrom a previous measurement, such as during step 278 (FIG. 15) of makingfinger-touch input system.

A moving time window can be applied to the negative-side high-passfiltered PMUT digital data 440. An illustrative moving time window 460,at a particular time, is shown in FIG. 18. Moving time window 460 has apredetermined duration 462 and a predetermined dynamic range 464. In theexample shown, the predetermined duration 462 is 200 ms. It ispreferable that the predetermined duration be in a range of 100 ms to300 ms. In the example shown, the predetermined dynamic range 464corresponds to a difference between a minimum signal (data) 446 and thebaseline signal (data) (442 or 450). It is preferable to set thepredetermined dynamic range to be a dynamic range of the PMUT digitaldata (in this example, the negative-side high-pass filtered PMUT digitaldata) under application of a standard force in a range of 0.5 N to 10 Nat the sense region. Similarly, a moving time window (490) can beapplied to the positive-side high-pass filtered PMUT digital data.

Boolean data indicating a decrease, over time, in the PMUT digital datafrom the PMUT receivers (e.g., 144 in FIGS. 16 and 21) can be obtained.In this context, the decrease is a decrease exceeding a predeterminedthreshold. We refer to this Boolean data as “PMUT Triggered” Booleandata because it is an indication or suggestion of a finger-touch eventat the sense region corresponding to the PMUT receivers. The “PMUTTriggered” Boolean data are obtained from the time-varying PMUT digitaldata. A moving time window (500, 460) can be applied to PMUT digitaldata before high-pass filtering 420 or to negative-side high-passfiltered PMUT digital data 440. In the examples shown, the change ofPMUT digital data U(t) in the moving time window (460 or 500) is thedifference in vertical axis values at a point (466 or 506) at the end ofthe respective time windows 460, 500 and a point (468 or 508) at thebeginning of the respective time windows 460, 500. As shown in FIG. 18,the PMUT digital data U(t) is decreasing in the respective time windows(460 or 500). A minimum decrease percentage (threshold) is set to be atleast 1%, and preferably at least 2%, of the predetermined dynamicrange. If the PMUT digital data U(t) decreases by at least the minimumdecrease percentage of the predetermined dynamic range in the movingtime window of the predetermined duration, “PMUT Triggered” is set toTrue. If the PMUT digital data U(t) does not decrease by at least theminimum decrease percentage of the predetermined dynamic range in themoving time window of the predetermined duration, “PMUT Triggered” isset to False. The moving time window can be applied to PMUT digital datathat exhibit a decrease in signal in response to an object contactingthe sense region.

FIG. 19 shows a graphical plot 510 of illustrative PMUT digital dataduring a repetitive touch event. Graphical plot 510 has a horizontalaxis 512 showing time t, in which 1 division corresponds to 2.0 sec, anda vertical axis 514 showing PMUT digital data, after ADC and beforehigh-pass filtering. Graphical plot 510 includes plot sections 516, 518,and 520 (ordered sequentially). Graphical plot portions 516 and 520correspond to time periods during which there is nothing touching orcoming into contact with the sense region. These graphical plot sections516 and 520 show the baseline signal. Plot section 518 corresponds torepetitive pressing of a digit (e.g., a finger) on the sense region,wherein each valley 522 in the PMUT signal corresponds to one occurrenceof the digit pressing at the sense region. In the example shown, plotsection 518 shows 10 repetitions of the digit pressing at the senseregion. After each repetition, the digit is completely released(removed) from the sense region. As shown in FIG. 19, the 10 repetitionsof the digit pressing at the sense region occur during a time period ofapproximately 4.1 sec. Accordingly, the repetition rate is approximately2.4 Hz.

FIG. 20 shows a graphical plot 530 of illustrative PMFE digital dataduring the repetitive touch event shown in FIG. 19. Graphical plot 530has a horizontal axis 532 showing time t, in which 1 divisioncorresponds to 2.0 sec, and a vertical axis 534 showing PMFE digitaldata. Graphical plot 530 includes plot sections 536, 538, and 540(ordered sequentially). Graphical plot portions 536 and 540 correspondto time periods during which there is nothing touching or coming intocontact with the sense region. These graphical plot sections 536 and 540show the baseline signal. Plot section 538 corresponds to repetitivepressing of a digit (e.g., a finger) on the sense region, analogous toplot section 518 of FIG. 19. There is a pair of maximum PMFE digitaldata 542 and a minimum PMFE digital data 544 (occurring after 542)corresponding to one repetition of a digit pressing at the sense regionand the digit being removed from the sense region. As the digit pressesthe sense region, the PMFE(s) undergo a first deformation resulting in afirst PMFE signal, and as the digit is removed from the sense region,the PMFE(s) undergo a second deformation resulting in a second PMFEsignal. In this case, the first and second deformations are in oppositedirections and the first and second PMFE signals are of oppositepolarities relative to the baseline signal. As illustrated in theexample of FIG. 11, the first deformation can be a first deflectionduring which a first deflection voltage V_(d1) (corresponding to strainof a certain polarity and magnitude) is detectable. The seconddeformation can be a second deflection during which a second deflectionvoltage V_(d2) (corresponding to strain of a certain polarity andmagnitude) is detectable. As shown in FIG. 20, the 10 repetitions of thedigit pressing at the sense region occur during a time period ofapproximately 4.1 sec. Accordingly, the repetition rate is approximately2.4 Hz.

FIG. 21 is a block diagram of the FMTSIC 20, which is an example of aforce-measuring and touch-sensing integrated circuit. FMTSIC 20 includesa MEMS portion 134 and signal processing circuitry 137 (in the ASICportion). The MEMS portion 134 includes PMUT transmitters 142, PMUTreceivers 144, and PMFEs 146. Signal processing circuitry 137 includes ahigh-voltage domain and a low-voltage domain. The high-voltage domain iscapable of operating at higher voltages required for driving the PMUTtransmitters. The high-voltage domain includes high-voltage transceivercircuitry 282, including high-voltage drivers. The high-voltagetransceiver circuitry 282 is electrically connected to the first PMUTelectrodes and the second PMUT electrodes of the PMUT transmitters. Thehigh-voltage transceiver is configured to output voltage pulses of 5 Vor greater, depending on the requirements of the PMUT transmitters. Thelow-voltage domain includes amplifiers (292, 302), analog-to-digitalconverters (ADCs) (296, 306), and processing circuit blocks 288. Theprocessing circuit blocks 288 can include microcontrollers (MCUs),memories, and digital signal processors (DSPs), for example. There maybe additional processing circuits located off-chip that are connected tothe processing circuit blocks 288. Such additional processing circuitscan be contained in other ICs 114 in FIG. 1.

The processing circuit blocks 288 are electrically connected to thehigh-voltage transceiver circuitry 282 and the ADCs (296, 306). Theprocessing circuit blocks 288 generate time-varying signals that aretransmitted to the high-voltage transceiver circuitry 282. Thehigh-voltage transceiver circuitry transmits high-voltage signals to thePMUT transmitters 142 in accordance with the time-varying signals fromthe processing circuit blocks. Voltage signals output by the PMUTreceivers 144 reach amplifiers 302 that are electrically connected toPMUT receivers 144 and get amplified by the amplifiers 302. Theamplified voltage signals are sent to ADC 306 to be converted to digitalsignals (PMUT digital data) which can be processed or stored by theprocessing circuit blocks 288. Similarly, voltage signals output byPMFEs 146 reach amplifiers 292 that are electrically connected to PMFEs146 and get amplified by the amplifiers 292. These amplified voltagesignals are sent to ADC 296 to be converted to digital signals (PMFEdigital data) which can be processed or stored by processing circuitblocks 288.

A touch-input system can be implemented in a smartphone for example. Asmartphone 600 is shown in FIGS. 22, 23, and 24. FIG. 22 shows a housing602 including a front face 610 and a flat panel display 604. FIG. 23shows a bottom face 606 of the housing 602. FIG. 24 shows a side face608 of the housing, extending between the front face 610 and the backface 611. For FIGS. 22, 23, and 24, X-axis 612, Y-axis 614, and Z-axis616 are shown to illustrate the relative orientations of the elements ofthe smartphone 600. There are virtual buttons 622, 624, and 626(collectively, 620) corresponding to respective regions of the side face608. These virtual buttons 620 are distinguished from mechanical buttonsthat might be embedded in respective openings in the side face 608.There are no cut-out openings in the side face 608 corresponding to thevirtual buttons 620. A virtual button corresponds to a sense region ofone or more FMTSICs at the virtual button. The smartphone 600 includes ahaptic transducer 618. Typically, the haptic transducer 618 is embeddedinside the smartphone 600 and is not visible from the outside.

FIG. 25 shows schematic views of certain elements of a touch-inputsystem (or sub-system) 628. The touch-input system 628 includes thehousing 602 (the side face 608 and the virtual buttons 622, 624, and 626are shown). The virtual buttons 622, 624, and 626 are separated fromeach other by respective distances 623, 625, which are preferablygreater than a finger-touch zone. The touch-input system 628additionally includes a plurality of force-measuring and touch-sensingintegrated circuits (FMTSICs), an elongate flexible circuit 630 whichincludes digital bus wiring 648, and a host controller 634. For example,the digital bus wiring 648 can implement the I²C protocol. In theexample shown, there are three FMTSICs (642, 644, and 646), with each ofthe FMTSICs corresponding to a respective one of the virtual buttons(622, 624, and 626). The FMTSICs (642, 644, and 646) are mounted to theelongate flexible circuit 630 at a respective position thereof and arecoupled to the digital bus wiring 648. The host controller 634 is incommunication with each of the FMTSICs via the digital bus wiring 648.In the example shown, the host controller 634 is implemented as anintegrated circuit (IC) and is mounted to a widened portion 636 of theelongate flexible circuit. In other examples, the host controller can beanother microprocessor or microcontroller, such as a main microprocessorof a smartphone or other electronic apparatus.

For ease of illustration, FIG. 25 shows the side face 608 and elongateflexible circuit 630 laterally displaced from each other. In actualimplementation, the side face 608 and elongate flexible circuit 630would overlap. The side face 608 of the housing 602 is an example of acover layer (FIG. 1). In this case, the cover layer is a portion (i.e.,the side face portion) of the housing. In other cases, the housing maybe a component separate from the cover layer, and the housing and thecover layer may be attached to each other such that forces applied tothe housing are transmitted to the cover layer. We refer to both casesas the housing being mechanically coupled to the cover layer. TheFMTSICs are coupled to the inner surface of the cover layer (housing) ata respective position, such that each of the FMTSICs corresponds to arespective one of the virtual buttons, and each of the virtual buttonscorresponds to a respective region of the cover layer.

In the example shown, the FMTSICs (642, 644, and 646) are arrayed alonga longitudinal direction 638 of the elongate flexible circuit 630. EachFMTSIC typically has a lateral dimension (in FIG. 25, along the Y-axis614 or along the Z-axis 616) of 3 mm or less, or 2.6 mm or less.Preferably, all of the analog data measured at the FMTSICs are convertedto digital data at the respective FMTSIC and the data transmittedbetween the respective FMTSIC and the host controller can be entirelydigital data. This precludes the need for any analog data wiring betweenthe FMTSICs and the host controller. Accordingly, it is possible for awidth 632 of the elongate flexible circuit 630 along a transversedirection (along Z-axis 616) at one or more of the FMTSICs (642, 644,646) to be no greater than 3 mm. In the case that the host controller isimplemented as a host controller IC mounted to the elongate flexiblecircuit, there would be no need for any analog input/output pin on thehost controller IC.

FIG. 26 shows schematic views of certain elements of a touch-inputsystem (or sub-system) 629, which is similar to touch input system 628(FIG. 25) in some respects. Touch-input system 629 differs from touchinput system 628 in that there are six FMTSICs (642, 643, 644, 645, 646,and 647). There are two FMTSICs corresponding to a respective one of thevirtual buttons. FMTSICs 642 and 643 correspond to VB 622, FMTSICs 644and 645 correspond to VB 624, and FMTSIC 646 and 647 correspond to VB626. There can be two or more FMTSICs corresponding to each of thevirtual buttons. In the case that there are two or more FMTSICscorresponding to one virtual button, such FMTSICs are preferablyseparated from each other by a distance smaller than a finger-touchzone.

FIG. 27 is a schematic diagram of a user-input system 650, whichincludes a touch-input sub-system 652, a haptic controller 654, and ahaptic transducer 656. The touch-input sub-system 650 additionallyincludes a cover layer, which is not shown. For example, the user-inputsystem 650 can be implemented in a smartphone 600 (FIGS. 22, 23, 24).The touch-input sub-system 652 includes a plurality of FMTSICs 642, 644,646. Each of the FMTSICs is coupled to (attached to) the inner surfaceof the cover layer at a respective position. Each FMTSIC (642, 644, 646)corresponds to one of a plurality of virtual button (622, 624, 626).Each of the virtual buttons 622, 624, 626 corresponds a respectiveregion of the cover layer. In the example shown, the touch-inputsub-system 652 is implemented with one FMTSIC per virtual button,similar to the arrangement shown in FIG. 25. Alternatively, touch-inputsub-system 652 can be implemented with two (or more) FMTSICs per virtualbutton, similar to the arrangement shown in FIG. 26. In the smartphoneexample, the haptic transducer 618 is embedded in the smartphone but isnot necessarily attached to the cover layer, which corresponds to theside face 608 of the smartphone housing 602. Nevertheless, the haptictransducer is vibrationally coupled to the cover layer, which means thatvibrations from the haptic transducer 618 are transmitted to the coverlayer, such that a finger touching the cover layer can sense thevibrations (the haptic feedback).

The haptic controller 654 and the haptic transducer 618 are coupled to(connected to) each other via wiring 664. The haptic controller 654 isconfigured to drive the haptic transducer 618 to generate hapticfeedback in accordance with haptic feedback commands. In the examplesshown in FIGS. 27 and 28, the haptic controller 654 is coupled to thetouch-input sub-system (652, 662), enabling it to receive hapticfeedback commands from the touch-input sub-system (652, 662). In theexample of touch-input system 650 (FIG. 27), the haptic controller 654is coupled to (connected to) the individual FMTSICs (642, 644, 646) viawiring 658. In this example, the individual FMTSICs (more specifically,the signal processing circuitry of the individual FMTSICs) determinehaptic feedback commands, which are transmitted to the haptic controller654 via wiring 658. In the example of touch-input system 660 (FIG. 28),the haptic controller 654 is coupled to (connected to) the hostcontroller 634 via wiring 668. In this example, the host controller 634transmits haptic feedback commands to the haptic controller 654. Thehaptic feedback commands can be determined at the individual FMTSICsfrom the respective PMFE data and PMUT data and be transmitted to thehost controller 634, or the haptic feedback commands can be determinedat the host controller 634 in accordance with PMFE data and PMUT datareceived from the individual FMTSICs. The touch-input system 660 (FIG.28) differs from touch-input system 650 (FIG. 27) in the connection of(coupling of) the haptic controller 654 to the respective touch-inputsub-system (662, 652).

FIG. 29 is a schematic diagram of a user-input system 670, whichincludes a processor 674. Whereas the host controller 634 (FIGS. 25, 26,27, and 28) is primarily configured to control operation of the FMTSICsand process data to and from the FMTSICs, this processor 674 can be ageneral-purpose processor. The processor 674 is coupled to thetouch-input sub-system 672 via wiring 676. FIGS. 25, 26, 27, and 28illustrate examples of possible touch-input sub-systems 672. Hapticcontroller 654 is coupled to the touch-input sub-system 672 (via wiring678) and/or to the processor 674 (via wiring 682). In one example,haptic feedback commands can be determined (generated) at thetouch-input sub-system 672 and be transmitted to the haptic controller654 via wiring 678. In another example, PMUT digital data and PMFEdigital data can be transmitted from the touch-input sub-system 672 tothe processor 674 (via wiring 676), haptic feedback commands can bedetermined at the processor 674 in accordance with the PMUT digital dataand the PMFE digital data, and the haptic feedback commands can betransmitted from the processor 674 to the haptic controller 654. Fromthe user's point of view, it is preferable to reduce the latency timesfor haptic feedback as much as possible. Typically, shorter latencytimes can be achieved by determining the haptic feedback commands at thetouch-input sub-system (e.g., at the host controller or the signalprocessing circuitry in the FMTSICs) and transmitting the hapticfeedback commands from the touch-input sub-system to the hapticcontroller than by determining the haptic feedback commands at aprocessor 674 and transmitting the haptic feedback commands from theprocessor 674 to the haptic controller 654.

Touch inputs can be determined in the user-input system 670 of FIG. 29.In one example, touch inputs can be determined at the touch-inputsub-system 672 and be transmitted to the processor 674 via wiring 676.In another example, PMUT digital data and PMFE digital data can betransmitted from the touch-input sub-system 672 to the processor 674(via wiring 676), and touch inputs can be determined at the processor674 in accordance with the PMUT digital data and the PMFE digital data.Let us suppose that a finger presses at the cover layer in a region ofone of the virtual buttons, corresponding to a touch input of “decreasevolume”. The processor receives the touch input “decrease volume” andexecutes an action in accordance with the touch input (e.g., decreasespeaker volume of the smartphone). The touch input “decrease volume” isan example of a primary touch input. A primary touch input is a touchinput that is actionable by itself. As mentioned above, haptic feedbackcommands can be determined in the user-input system 670. We refer tohaptic feedback commands that are associated with primary touch inputsas primary haptic feedback commands. We refer to haptic feedbackcommands other than those associated with primary touch inputs assupplemental haptic feedback commands.

FIG. 30 is a schematic diagram of a user-input system 680. It differsfrom user-input system 670 in that there is another input sub-system684. Processor 674 is additionally coupled to the other input sub-system684 via wiring 686. There are numerous possible examples of the otherinput sub-system. For example, such a sub-system can include one or moreof the following: image sensor, gyroscope, microphone, touch displaypanel, infrared (IR) sensor, temperature sensor, humidity sensor,pressure sensor, compass, keyboard, and joystick. One or more of thesesub-systems may be included in a smartphone, smart watch, or otherelectronic apparatus.

Consider a first operating mode of the user-input system 680 (FIG. 30).In the first mode, the primary touch inputs from the touch-inputsub-system 672 and the primary inputs from the other input sub-system684 are independent of each other. Consider the example in which afinger presses the cover layer at a region of one of the virtualbuttons, corresponding to a primary touch input of “decrease volume”.The processor receives the primary touch input “decrease volume” andexecutes an action in accordance with the primary touch input (e.g.,decrease speaker volume of the smartphone). Consider an example in whichthe other input sub-system is a touch display panel. Suppose that thetouch display panel is displaying a virtual keyboard and the userselects the letter “a”. The processor 674 receives the primary input “a”from the other input sub-system (touch display panel) and executes anaction in accordance with the primary input (e.g., add letter “a” to atext displayed on the touch display panel). The primary touch input andthe primary input are independent of each other.

In the first mode, the touch-input sub-system 672 or the processor 674can determine primary haptic feedback commands in accordance withprimary touch inputs at the virtual buttons and transmit these touchhaptic feedback commands to the haptic controller 654.

Consider a second operating mode of the user-input system 680 (FIG. 30).In the second mode, the touch inputs from the touch-input sub-system 672can be supplemental touch inputs or primary touch inputs. Supplementaltouch inputs are “supplemental” in the sense that they supplement theprimary inputs, which are from the other input sub-system 684. Thesupplemental touch inputs are not actionable by themselves. Theprocessor 674 determines combined inputs in accordance with the primaryinputs from the other input sub-system 684 and the supplemental touchinputs from the touch-input sub-system 672.

The touch-input sub-system (650, 660, 672) or the processor (674) candetermine supplemental touch inputs and primary touch inputs dependingon whether a region of the cover layer corresponding to a virtual buttonis not touched, lightly touched, or pressed. For brevity, we sometimesrefer to touching (or lightly touching or pressing) of a region of thecover layer corresponding to an FMTSIC as touching (or lightly touchingor pressing) of the respective FMTSIC even though the finger does notactually directly touch (or lightly touch or press) the respectiveFMTSIC. The touch-input sub-system or the processor determines a primarytouch input if at least one of the FMTSICs is pressed (i.e., touchedwith a force greater than “lightly touched”). The touch-input sub-systemor the processor determines a supplemental touch input if at least oneof the FMTSICs is lightly touched or if none of the FMTSICs is touched.We refer to the supplemental touch input in the case of at least one ofthe FMTSICs being lightly touched as “first supplemental touch input.”We refer to the supplemental touch input in the case of none of theFMTSICs being touched as “zeroth supplemental touch input.” Hapticfeedback commands associated with supplemental touch inputs are includedin supplemental haptic feedback commands.

The criteria for primary touch inputs, zeroth supplemental touch inputs,and first supplemental touch inputs can be stated more specifically asfollows: (1) the touch-input sub-system or the processor is configuredto determine zeroth supplemental touch inputs if “PMUT Triggered”Boolean data is False for all of the FMTSICs; (2) the touch-inputsub-system or the processor is configured to determine firstsupplemental touch inputs and optionally determine supplemental hapticfeedback commands if “PMUT Triggered” Boolean data is True for at leastone of the FMTSICs (Touched FMTSICs) and light-force conditions aresatisfied for all of the Touched FMTSICs; and (3) the touch-inputsub-system or the processor is configured to determine primary touchinputs and optionally determine primary haptic feedback commands if“PMUT Triggered” Boolean data is True for at least one of the FMTSICs(Touched FMTSICs) and light-force conditions are not satisfied for atleast one of the Touched FMTSICs. Here, the light-force conditions ofeach of the FMTSICs include: the PMFE digital data of the respectiveFMTSIC indicates an applied force less than a light-force thresholdF_(light). The light-force threshold F_(light) is preferably 150grams-force or less. The implementations shown in FIGS. 25, 26, 27, and28 can determine zeroth supplemental touch inputs, first supplementaltouch inputs, and primary touch inputs because of the availability ofboth PMUT data and PMFE data. Conventional touch-input systems relyingonly on PMUT data are not able to readily measure an applied force anddetermine whether the applied force is less than light-force thresholdF_(light).

To illustrate the second operating mode, consider an example in whichthe other input sub-system is a touch display panel. Suppose that thetouch display panel is displaying a plurality of software applicationicons and the user selects the camera icon. The processor 674 receivesthe primary input “standard camera selected” from the other inputsub-system (touch display panel). There is a primary touch input of“decrease volume” if first FMTSIC 642 (first virtual button 622) ispressed, a primary touch input of “increase volume” if second FMTSIC 644(second virtual button 624) is pressed, and a primary touch input of“silence” if third FMTSIC 642 (third virtual button 622) is pressed. Ifone of the FMTSICs (642, 644, 646) is lightly touched, there are firstsupplemental touch inputs. If none of the FMTSICs (642, 644, 646) istouched, there are zeroth supplemental touch inputs. Some examples ofcombined inputs determined in accordance with the primary inputs andfirst supplemental touch inputs or zeroth supplemental touch inputs areshown in Table 1 herein. In the example shown, a combined inputdetermined in accordance with a zeroth supplemental touch input and aprimary input is unchanged from the primary input (e.g., standard cameraselected). When combined inputs are determined in accordance with firstsupplemental touch inputs and primary inputs, the combined inputs can bedifferent from each other and from the primary input. For example: (1)combined input is “long-zoom camera selected” based on a firstsupplemental touch input at the first virtual button 622 (FMTSIC 642 islightly touched) and a primary input of “standard camera selected”; (2)combined input is “macro-lens camera selected” based on a firstsupplemental touch input at the second virtual button 624 (FMTSIC 644 islightly touched) and a primary input of “standard camera selected”; and(3) combined input is “night-vision infrared camera selected” based on afirst supplemental touch input at the third virtual button 626 (FMTSIC646 is lightly touched) and a primary input of “standard cameraselected”.

TABLE 1 Combined Combined input = First input = Zeroth supplementaltouch supplemental touch Virtual Primary touch input + Primary input +Primary button input input input 1 Decrease volume Long-zoom cameraStandard camera 2 Increase volume Macro-lens camera Standard camera 3Silence Night-vision Standard camera infrared camera

The present user-input systems employ virtual buttons, which correspondto respective regions of the cover layer. Contrary to physical buttons,there may be no physical demarcation of a virtual button. Accordingly,it may be desirable to delineate a location of a virtual button byhaptic feedback. In this use case, a finger may lightly touch areascorresponding to the virtual buttons when searching for the location ofa virtual button. If an area corresponding to a virtual button islightly touched, the touch-input sub-system (650, 660, 672) or theprocessor (674) can determine supplemental haptic feedback commands ifat least one of the FMTSICs is lightly touched. On the other hand, if atleast one of the FMTSICs is pressed, the touch-input sub-system or theprocessor can determine primary touch inputs and optionally determineprimary haptic feedback commands associated with the primary touchinput. The haptic controller is configured to drive the haptictransducer to generate haptic feedback in accordance with the primaryhaptic feedback commands and the supplemental haptic feedback commands.The haptic feedback in accordance with the supplemental feedbackcommands delineate the location of the virtual button.

A user-input system (e.g., 650, 660, 670, 680) can be used to carry outmethods of delineating a location of a virtual button by hapticfeedback. The methods are illustrated using the flow diagram in FIG. 31.Method 700 (FIG. 31) includes steps 702, 704, 706, 708, 710, 712, 714,718, 720, 722, 724, 726, and 728. Step 702 relates generally toconfiguring the user-input system, as explained with reference to FIGS.27, 28, 29, and 30. Step 702 includes configuring a cover layer havingan outer surface which can be touched by a finger and an inner surfaceopposite the outer surface, such that each of the virtual buttonscorrespond to a respective region of the cover layer. Step 702 includesconfiguring a touch-input sub-system. The touch-input sub-systemincludes the cover layer and a plurality of force-measuring andtouch-sensing integrated circuits (FMTSICs). Each of the FMTSICs iscoupled to the inner surface of the cover layer at a respectiveposition, and each of the FMTSICs corresponds to one of the virtualbuttons. Step 702 additionally includes configuring a haptic transducervibrationally coupled to the cover layer. Step 702 additionally includesconfiguring a haptic controller to drive the haptic transducer, coupledto the touch-input sub-system.

At step 704, an event occurs. Some examples of an event are as follows:(1) a finger lightly touching the cover layer at a virtual button, (2) afinger contacting and sliding along the cover layer including an area ofa virtual button, and (3) a finger pressing against the cover layer witha force stronger than lightly touching. Events can occur repeatedly. Anevent can also be a false-trigger event. An example of a false-triggerevent is a liquid droplet landing on the cover layer at a virtualbutton.

Method 700 has two branches: a first branch relating to operation of thePMUTs (PMUT transmitters and PMUT receivers) at steps 706, 708, and 710and a second branch relating to operation of the PMFEs at steps 712 and714. The first and second branches are carried out concurrently andrepeatedly. An event (step 704) can occur at some time while the firstand second branches are being carried out. At step 706, the PMUTtransmitters of each of the FMTSICs transmit ultrasound signals towardsthe cover layer. At least some of the ultrasound signals are reflectedat the outer surface of the cover layer, resulting in reflectedultrasound signals. Voltage signals are output by the PMUT receivers ofeach of the FMTSICs (PMUT voltage signals) in response to reflectedultrasound signals arriving from the cover layer. At step 710, the PMUTvoltage signals at each of the FMTSICs are converted by the signalprocessing circuitry of the respective FMTSIC to PMUT digital data. Atstep 712, voltage signals are output by the PMFEs of each of the FMTSICs(PMFE voltage signals) in response to a low-frequency mechanicaldeformation at the respective FMTSIC. At step 714, the PMFE voltagesignals at each of the FMTSICs are converted by the signal processingcircuitry of the respective FMTSIC to PMFE digital data.

The touch-input sub-system determines primary touch inputs (step 722) if“PMUT Triggered” Boolean data is True for at least one of the FMTSICs(Yes branch at step 718) (we refer to the at least one FMTSIC as“Touched FMTSICs”) and light-force conditions are not satisfied for atleast one of the Touched FMTSICs (No branch at step 720). Thelight-force conditions of each of the FMTSICs include the followingcondition: the PMFE digital data of the respective FMTSIC indicates anapplied force less than a light-force threshold F_(light). Thelight-force threshold is set such that a finger touching the senseregion (virtual button) with an applied force less than the light-forcethreshold F_(light) is lightly touching the sense region and notpressing against the sense region. Preferably, the light-force thresholdF_(light) is chosen to be 150 grams-force or less. If the light-forceconditions are not satisfied for at least one of the Touched FMTSICs (Nobranch at step 720), there is a “heavy-force” touch at the virtualbutton, such as a single press or a repetitive press, and thetouch-input sub-system determines primary touch inputs in accordancewith the touch at the virtual button.

The touch-input sub-system determines supplemental haptic feedbackcommands (step 726) if “PMUT Triggered” Boolean data is True for atleast one of the FMTSICs (Yes branch at step 718) (“Touched FMTSICs”)and light-force conditions are satisfied for all of the Touched FMTSICs(Yes branch at step 720). If the light-force conditions are satisfiedfor all of the Touched FMTSICs (Yes branch at step 720), there is a“light-force” touch at the virtual button(s) indicating that a finger issearching a location of a virtual button. The touch-input sub-systemcommunicates the supplemental haptic feedback commands to the hapticcontroller. The haptic controller drives the haptic transducer togenerate haptic feedback in accordance with the supplemental hapticfeedback commands. Haptic feedback generated in accordance withsupplemental haptic feedback commands delineates a location of at leastone of the virtual buttons.

The touch-input sub-system optionally determines primary haptic feedbackcommands (step 724) if “PMUT Triggered” Boolean data is True for atleast one of the FMTSICs (Yes branch at step 718) (“Touched FMTSICs”)and light-force conditions are not satisfied for at least one of theTouched FMTSICs (No branch at step 720). The touch-input sub-systemcommunicates the primary haptic feedback commands to the hapticcontroller. The haptic controller drives the haptic transducer togenerate haptic feedback in accordance with the primary haptic feedbackcommands. If primary haptic feedback commands are generated, it ispreferable to choose them such that haptic feedback generated inaccordance with primary haptic feedback commands and haptic feedbackgenerated in accordance with supplemental haptic feedback commands arenoticeably different. Preferably, the haptic feedback are noticeablydifferent in one or more of the following: amplitude, frequency, andpattern.

The touch-input sub-system optionally determines that there is no touchor there are no touched virtual buttons (step 728) if “PMUT Triggered”Boolean data is False for all of the FMTSICs (No branch at step 718).

The touch-input sub-system is configured to determine supplementalhaptic feedback commands if “PMUT Triggered” Boolean data is True for atleast one of the FMTSICs (Touched FMTSICs) and light-force conditionsare satisfied for all of the Touched FMTSICs. The touch-input sub-systemis configured to determine primary touch inputs and optionally determineprimary haptic feedback commands if “PMUT Triggered” Boolean data isTrue for at least one of the FMTSICs (Touched FMTSICs) and light-forceconditions are not satisfied for at least one of the Touched FMTSICs.The haptic controller is configured to drive the haptic transducer togenerate haptic feedback in accordance with the primary haptic feedbackcommands and the supplemental haptic feedback commands. Haptic feedbackgenerated in accordance with supplemental haptic feedback commandsdelineates a location of at least one of the virtual buttons.

In the example shown in FIG. 28, the touch-input sub-system 662 includesa host controller 634, in communication with each of the FMTSICs 642,644, 646 via digital bus wiring 648. The host controller can beconfigured to determine one or more of the following: supplementalhaptic feedback commands, primary haptic feedback commands, and primarytouch inputs. Additionally, or alternatively, the signal processingcircuitries of the FMTSICs can be configured to determine one or more ofthe following: supplemental haptic feedback commands, primary hapticfeedback commands, and primary touch inputs.

A user-input system that includes a processor (e.g., 670, 680) can beused to carry out method 700 of delineating a location of a virtualbutton by haptic feedback. In this implementation, step 702 additionallyincludes configuring a processor coupled to the touch-input sub-system.Step 702 additionally includes configuring a haptic controller, coupledto the touch-input sub-system and to the processor. In thisimplementation, the touch-input sub-system or the processor isconfigured to determine supplemental haptic feedback commands if “PMUTTriggered” Boolean data is True for at least one of the FMTSICs (TouchedFMTSICs) and light-force conditions are satisfied for all of the TouchedFMTSICs. The touch-input sub-system or the processor is configured todetermine primary touch inputs and optionally determine primary hapticfeedback commands if “PMUT Triggered” Boolean data is True for at leastone of the FMTSICs (Touched FMTSICs) and light-force conditions are notsatisfied for at least one of the Touched FMTSICs.

Method 700 can be carried out with a user-input system that includes aprocessor (e.g., 670, 680). In this implementation, step 702additionally includes configuring a processor coupled to the touch-inputsub-system. Step 702 additionally includes configuring a hapticcontroller, coupled to the touch-input sub-system and to the processor.The touch-input sub-system or the processor determines primary touchinputs (step 722) if “PMUT Triggered” Boolean data is True for at leastone of the FMTSICs (Yes branch at step 718) (“Touched FMTSICs”) andlight-force conditions are not satisfied for at least one of the TouchedFMTSICs (No branch at step 720). The touch-input sub-system or theprocessor determines supplemental haptic feedback commands (step 726) if“PMUT Triggered” Boolean data is True for at least one of the FMTSICs(Yes branch at step 718) (“Touched FMTSICs”) and light-force conditionsare satisfied for all of the Touched FMTSICs (Yes branch at step 720).The touch-input sub-system or the processor communicates thesupplemental haptic feedback commands to the haptic controller. Thehaptic controller drives the haptic transducer to generate hapticfeedback in accordance with the supplemental haptic feedback commands.The haptic controller is configured to drive the haptic transducer togenerate haptic feedback in accordance with the supplemental hapticfeedback commands. Haptic feedback generated in accordance withsupplemental haptic feedback commands delineates a location of at leastone of the virtual buttons.

The touch-input sub-system or the processor optionally determinesprimary haptic feedback commands (step 724) if “PMUT Triggered” Booleandata is True for at least one of the FMTSICs (Yes branch at step 718)(“Touched FMTSICs”) and light-force conditions are not satisfied for atleast one of the Touched FMTSICs (No branch at step 720). Thetouch-input sub-system or the processor communicates the primary hapticfeedback commands to the haptic controller. The haptic controller drivesthe haptic transducer to generate haptic feedback in accordance with theprimary haptic feedback commands. If primary haptic feedback commandsare generated, it is preferable to choose them such that haptic feedbackgenerated in accordance with primary haptic feedback commands and hapticfeedback generated in accordance with supplemental haptic feedbackcommands are noticeably different. Preferably, the haptic feedback arenoticeably different in one or more of the following: amplitude,frequency, and pattern.

The touch-input sub-system or the processor optionally determines thatthere is no touch or there are no touched virtual buttons (step 728) if“PMUT Triggered” Boolean data is False for all of the FMTSICs (No branchat step 718).

A method of determining user-input is illustrated using the flow diagramin FIG. 32. Method 730 (FIG. 32) includes steps 732, 704, 706, 708, 710,712, 714, 718, 720, 722, 724, 726, 734, 736, 738, and 740. Steps 704,706, 708, 710, 712, 714, 718, 720, 722, 724, and 726 have been describedwith reference to method 700 (FIG. 31). Step 732 relates generally toconfiguring the user-input system, as explained with reference to FIGS.27, 28, 29, and 30. Step 732 includes configuring a cover layer havingan outer surface which can be touched by a finger and an inner surfaceopposite the outer surface, such that each of the virtual buttonscorrespond to a respective region of the cover layer. Step 732 includesconfiguring a touch-input sub-system. The touch-input sub-systemincludes the cover layer and a plurality of force-measuring andtouch-sensing integrated circuits (FMTSICs). Each of the FMTSICs iscoupled to the inner surface of the cover layer at a respectiveposition, and each of the FMTSICs corresponds to one of the virtualbuttons. Step 732 additionally includes configuring another inputsub-system and configuring a processor coupled to the touch-inputsub-system and to the other input sub-system. Step 732 additionallyincludes configuring a haptic transducer vibrationally coupled to thecover layer. Step 732 additionally includes configuring a hapticcontroller to drive the haptic transducer, coupled to the processor andoptionally coupled to the touch-input sub-system.

The touch-input sub-system or the processor determines primary touchinputs (step 722) if “PMUT Triggered” Boolean data is True for at leastone of the FMTSICs (Yes branch at step 718) (“Touched FMTSICs”) andlight-force conditions are not satisfied for at least one of the TouchedFMTSICs (No branch at step 720).

The touch-input sub-system or the processor optionally determinesprimary haptic feedback commands (step 724) if “PMUT Triggered” Booleandata is True for at least one of the FMTSICs (Yes branch at step 718)(“Touched FMTSICs”) and light-force conditions are not satisfied for atleast one of the Touched FMTSICs (No branch at step 720). Thetouch-input sub-system or the processor communicates the primary hapticfeedback commands to the haptic controller. The haptic controller drivesthe haptic transducer to generate haptic feedback in accordance with theprimary haptic feedback commands.

The touch-input sub-system or the processor determines firstsupplemental touch inputs (step 734) if “PMUT Triggered” Boolean data isTrue for at least one of the FMTSICs (Yes branch at step 718) (“TouchedFMTSICs”) and light-force conditions are satisfied for all of theTouched FMTSICs (Yes branch at step 720). If the first supplementaltouch inputs are determined by the touch-input sub-system, the firstsupplemental touch inputs are transmitted to the processor. Inputs fromthe other input sub-system are transmitted to the processor. Theprocessor determines combined inputs in accordance with primary inputsfrom the other input sub-system and the first supplemental touch inputs(step 736).

The touch-input sub-system or the processor determines zerothsupplemental touch inputs (step 738) if “PMUT Triggered” Boolean data isFalse for all of the FMTSICs (No branch at step 718) (“Touched FMTSICs”)and light-force conditions are satisfied for all of the Touched FMTSICs(Yes branch at step 720). If the zeroth supplemental touch inputs aredetermined by the touch-input sub-system, the zeroth supplemental touchinputs are transmitted to the processor. Primary inputs from the otherinput sub-system are transmitted to the processor. The processordetermines combined inputs in accordance with primary inputs from theother input sub-system and the zeroth supplemental touch inputs (step740). The processor determines combined inputs in accordance with (1)primary inputs from the other input sub-system and (2) the zerothsupplemental touch inputs or the first supplemental touch inputs (steps736, 740). The most recently obtained supplemental touch input, whetherit is a zeroth supplemental touch input or a first supplemental touchinput, is used to determine the combined input. Preferably, the combinedinputs that result from the first supplemental touch inputs and zerothsupplemental touch inputs are different (see Table 1 example).

The touch-input sub-system or the processor optionally determinessupplemental haptic feedback commands (step 726) if “PMUT Triggered”Boolean data is True for at least one of the FMTSICs (Yes branch at step718) (“Touched FMTSICs”) and light-force conditions are satisfied forall of the Touched FMTSICs (Yes branch at step 720). The touch-inputsub-system communicates the supplemental haptic feedback commands to thehaptic controller. The haptic controller drives the haptic transducer togenerate haptic feedback in accordance with the supplemental hapticfeedback commands. If primary haptic feedback commands and supplementalhaptic feedback commands are generated, it is preferable to choose themsuch that haptic feedback generated in accordance with primary hapticfeedback commands and haptic feedback generated in accordance withsupplemental haptic feedback commands are noticeably different.Preferably, the haptic feedback are noticeably different in one or moreof the following: amplitude, frequency, and pattern.

A user-input system (e.g., 680) can be used to carry out method 730. Theuser-input system can be configured as follows. The touch-inputsub-system or the processor is configured to determine zerothsupplemental touch inputs if “PMUT Triggered” Boolean data is False forall of the FMTSICs. The touch-input sub-system or the processor isconfigured to determine first supplemental touch inputs and optionallydetermine supplemental haptic feedback commands if “PMUT Triggered”Boolean data is True for at least one of the FMTSICs (Touched FMTSICs)and light-force conditions are satisfied for all of the Touched FMTSICs.The touch-input sub-system or the processor is configured to determineprimary touch inputs and optionally determine primary haptic feedbackcommands if “PMUT Triggered” Boolean data is True for at least one ofthe FMTSICs (Touched FMTSICs) and light-force conditions are notsatisfied for at least one of the Touched FMTSICs. The haptic controlleris configured to drive the haptic transducer to generate haptic feedbackin accordance with the primary haptic feedback commands and thesupplemental haptic feedback commands. The processor is configured todetermine combined inputs in accordance with (1) primary inputs from theother input sub-system and (2) the zeroth supplemental touch inputs orthe first supplemental touch inputs. The light-force conditions of eachof the FMTSICs include the following condition: the PMFE digital data ofthe respective FMTSIC indicates an applied force less than a light-forcethreshold F_(light). The light-force threshold is set such that a fingertouching the sense region (virtual button) with an applied force lessthan the light-force threshold F_(light) is lightly touching the senseregion and not pressing against the sense region. Preferably, thelight-force threshold F_(light) is chosen to be 150 grams-force or less.

What is claimed is:
 1. A user-input system for delineating a location ofa virtual button by haptic feedback, comprising: a touch-inputsub-system comprising a cover layer, having an outer surface which canbe touched by a finger and an inner surface opposite the outer surface,and a plurality of force-measuring and touch-sensing integrated circuit(FMTSIC), each of the FMTSICs coupled to the inner surface at arespective position, each of the FMTSICs corresponding to one of aplurality of virtual buttons, each of the virtual buttons correspondingto a respective region of the cover layer; a haptic transducervibrationally coupled to the cover layer; and a haptic controllercoupled to the touch-input sub-system; wherein each of the FMTSICscomprises: a semiconductor substrate; signal processing circuitry on thesemiconductor substrate; at least one piezoelectric micromechanicalforce-measuring element (PMFE); at least one piezoelectricmicromechanical ultrasonic transducer (PMUT) configured as a transmitter(PMUT transmitter); and at least one PMUT configured as a receiver (PMUTreceiver); the PMUT transmitters of each of the FMTSICs are configuredto transmit ultrasound signals towards the cover layer; the PMUTreceivers of each of the FMTSICs are configured to output voltagesignals (PMUT voltage signals) in response to reflected ultrasoundsignals arriving from the cover layer, the PMUT voltage signals beingconverted to PMUT digital data at the signal processing circuitry of therespective FMTSIC; and the PMFEs of each of the FMTSICs are configuredto output voltage signals (PMFE voltage signals) in accordance with atime-varying strain at respective portions of a piezoelectric layer atthe respective PMFEs resulting from a low-frequency mechanicaldeformation, the PMFE voltage signals being converted to PMFE digitaldata at the signal processing circuitry of the respective FMTSIC; thetouch-input sub-system is configured to determine supplemental hapticfeedback commands if “PMUT Triggered” Boolean data is True for at leastone of the FMTSICs (Touched FMTSICs) and light-force conditions aresatisfied for all of the Touched FMTSICs; the touch-input sub-system isconfigured to determine primary touch inputs and optionally determineprimary haptic feedback commands if “PMUT Triggered” Boolean data isTrue for at least one of the FMTSICs (Touched FMTSICs) and light-forceconditions are not satisfied for at least one of the Touched FMTSICs;the haptic controller is configured to drive the haptic transducer togenerate haptic feedback in accordance with the primary haptic feedbackcommands and the supplemental haptic feedback commands; haptic feedbackgenerated in accordance with supplemental haptic feedback commandsdelineates a location of at least one of the virtual buttons; thelight-force conditions of each of the FMTSICs comprise: the PMFE digitaldata of the respective FMTSIC indicates an applied force less than alight-force threshold F_(light); and the “PMUT Triggered” Boolean dataare obtained from the PMUT digital data.
 2. The system of claim 1,wherein the signal processing circuitries of the FMTSICs are configuredto determine one or more of the following: supplemental haptic feedbackcommands, primary haptic feedback commands, and primary touch inputs. 3.The system of claim 1, wherein the touch-input sub-system additionallycomprises a host controller, in communication with each of the FMTSICsvia digital bus wiring and configured to determine one or more of thefollowing: supplemental haptic feedback commands, primary hapticfeedback commands, and primary touch inputs.
 4. The system of claim 1,wherein there are two or more FMTSICs corresponding to each of thevirtual buttons.
 5. The system of claim 1, wherein the light-forcethreshold F_(light) is 150 grams-force or less.
 6. The system of claim1, wherein haptic feedback generated in accordance with primary hapticfeedback commands and haptic feedback generated in accordance withsupplemental haptic feedback commands are noticeably different in one ormore of the following: amplitude, frequency, and pattern.
 7. Auser-input system for delineating a location of a virtual button byhaptic feedback, comprising: a touch-input sub-system comprising a coverlayer, having an outer surface which can be touched by a finger and aninner surface opposite the outer surface, and a plurality offorce-measuring and touch-sensing integrated circuit (FMTSIC), each ofthe FMTSICs coupled to the inner surface at a respective position, eachof the FMTSICs corresponding to one of a plurality of virtual buttons,each of the virtual buttons corresponding to a respective region of thecover layer; a processor coupled to the touch-input sub-system; a haptictransducer vibrationally coupled to the cover layer; and a hapticcontroller coupled to the processor and optionally coupled to thetouch-input sub-system; wherein each of the FMTSICs comprises: asemiconductor substrate; signal processing circuitry on thesemiconductor substrate; at least one piezoelectric micromechanicalforce-measuring element (PMFE); at least one piezoelectricmicromechanical ultrasonic transducer (PMUT) configured as a transmitter(PMUT transmitter); and at least one PMUT configured as a receiver (PMUTreceiver); the PMUT transmitters of each of the FMTSICs are configuredto transmit ultrasound signals towards the cover layer; the PMUTreceivers of each of the FMTSICs are configured to output voltagesignals (PMUT voltage signals) in response to reflected ultrasoundsignals arriving from the cover layer, the PMUT voltage signals beingconverted to PMUT digital data at the signal processing circuitry of therespective FMTSIC; and the PMFEs of each of the FMTSICs are configuredto output voltage signals (PMFE voltage signals) in accordance with atime-varying strain at respective portions of a piezoelectric layer atthe respective PMFEs resulting from a low-frequency mechanicaldeformation, the PMFE voltage signals being converted to PMFE digitaldata at the signal processing circuitry of the respective FMTSIC; thetouch-input sub-system or the processor is configured to determinesupplemental haptic feedback commands if “PMUT Triggered” Boolean datais True for at least one of the FMTSICs (Touched FMTSICs) andlight-force conditions are satisfied for all of the Touched FMTSICs; thetouch-input sub-system or the processor is configured to determineprimary touch inputs and optionally determine primary haptic feedbackcommands if “PMUT Triggered” Boolean data is True for at least one ofthe FMTSICs (Touched FMTSICs) and light-force conditions are notsatisfied for at least one of the Touched FMTSICs; the haptic controlleris configured to drive the haptic transducer to generate haptic feedbackin accordance with the primary haptic feedback commands and thesupplemental haptic feedback commands; haptic feedback generated inaccordance with supplemental haptic feedback commands delineates alocation of at least one of the virtual buttons; the light-forceconditions of each of the FMTSICs comprise: the PMFE digital data of therespective FMTSIC indicates an applied force less than a light-forcethreshold F_(light); and the “PMUT Triggered” Boolean data are obtainedfrom the PMUT digital data.
 8. The system of claim 7, wherein the signalprocessing circuitries of the FMTSICs are configured to determine one ormore of the following: supplemental haptic feedback commands, primaryhaptic feedback commands, and primary touch inputs.
 9. The system ofclaim 7, wherein the touch-input sub-system additionally comprises ahost controller, in communication with each of the FMTSICs via digitalbus wiring and configured to determine one or more of the following:supplemental haptic feedback commands, primary haptic feedback commands,and primary touch inputs.
 10. The system of claim 7, wherein there aretwo or more FMTSICs corresponding to each of the virtual buttons. 11.The system of claim 7, wherein the light-force threshold F_(light) is150 grams-force or less.
 12. The system of claim 7, wherein hapticfeedback generated in accordance with primary haptic feedback commandsand haptic feedback generated in accordance with supplemental hapticfeedback commands are noticeably different in one or more of thefollowing: amplitude, frequency, and pattern.
 13. A user-input system,comprising: a touch-input sub-system comprising a cover layer, having anouter surface which can be touched by a finger and an inner surfaceopposite the outer surface, and a plurality of force-measuring andtouch-sensing integrated circuit (FMTSIC), each of the FMTSICs coupledto the inner surface at a respective position, each of the FMTSICscorresponding to one of a plurality of virtual buttons, each of thevirtual buttons corresponding to a respective region of the cover layer;another input sub-system; a processor coupled to the touch-inputsub-system and to the other input sub-system; a haptic transducervibrationally coupled to the cover layer; and a haptic controllercoupled to the processor and optionally coupled to the touch-inputsub-system; wherein each of the FMTSICs comprises: a semiconductorsubstrate; signal processing circuitry on the semiconductor substrate;at least one piezoelectric micromechanical force-measuring element(PMFE); at least one piezoelectric micromechanical ultrasonic transducer(PMUT) configured as a transmitter (PMUT transmitter); and at least onePMUT configured as a receiver (PMUT receiver); the PMUT transmitters ofeach of the FMTSICs are configured to transmit ultrasound signalstowards the cover layer; the PMUT receivers of each of the FMTSICs areconfigured to output voltage signals (PMUT voltage signals) in responseto reflected ultrasound signals arriving from the cover layer, the PMUTvoltage signals being converted to PMUT digital data at the signalprocessing circuitry of the respective FMTSIC; and the PMFEs of each ofthe FMTSICs are configured to output voltage signals (PMFE voltagesignals) in accordance with a time-varying strain at respective portionsof a piezoelectric layer at the respective PMFEs resulting from alow-frequency mechanical deformation, the PMFE voltage signals beingconverted to PMFE digital data at the signal processing circuitry of therespective FMTSIC; the touch-input sub-system or the processor isconfigured to determine zeroth supplemental touch inputs if “PMUTTriggered” Boolean data is False for all of the FMTSICs; the touch-inputsub-system or the processor is configured to determine firstsupplemental touch inputs and optionally determine supplemental hapticfeedback commands if “PMUT Triggered” Boolean data is True for at leastone of the FMTSICs (Touched FMTSICs) and light-force conditions aresatisfied for all of the Touched FMTSICs; the touch-input sub-system orthe processor is configured to determine primary touch inputs andoptionally determine primary haptic feedback commands if “PMUTTriggered” Boolean data is True for at least one of the FMTSICs (TouchedFMTSICs) and light-force conditions are not satisfied for at least oneof the Touched FMTSICs; the haptic controller is configured to drive thehaptic transducer to generate haptic feedback in accordance with theprimary haptic feedback commands and the supplemental haptic feedbackcommands; the processor is configured to determine combined inputs inaccordance with (1) primary inputs from the other input sub-system and(2) the zeroth supplemental touch inputs or the first supplemental touchinputs; the light-force conditions of each of the FMTSICs comprise: thePMFE digital data of the respective FMTSIC indicates an applied forceless than a light-force threshold F_(light); and the “PMUT Triggered”Boolean data are obtained from the PMUT digital data.
 14. The system ofclaim 13, wherein the signal processing circuitries of the FMTSICs areconfigured to determine one or more of the following: supplementalhaptic feedback commands, primary haptic feedback commands, and primarytouch inputs.
 15. The system of claim 13, wherein the touch-inputsub-system additionally comprises a host controller, in communicationwith each of the FMTSICs via digital bus wiring and configured todetermine one or more of the following: supplemental haptic feedbackcommands, primary haptic feedback commands, and primary touch inputs.16. The system of claim 13, wherein there are two or more FMTSICscorresponding to each of the virtual buttons.
 17. The system of claim13, wherein the light-force threshold F_(light) is 150 grams-force orless.
 18. The system of claim 13, wherein haptic feedback generated inaccordance with primary haptic feedback commands and haptic feedbackgenerated in accordance with supplemental haptic feedback commands arenoticeably different in one or more of the following: amplitude,frequency, and pattern.
 19. The system of claim 13, wherein the otherinput sub-system comprises one or more of the following: image sensor,gyroscope, microphone, touch display panel, infrared (IR) sensor,temperature sensor, humidity sensor, pressure sensor, compass, keyboard,and joystick.
 20. A method of delineating a location of a virtual buttonby haptic feedback, comprising: (A1) configuring a touch-inputsub-system comprising a cover layer having an outer surface, which canbe touched by a finger and an inner surface opposite the outer surface,and a plurality of force-measuring and touch-sensing integrated circuits(FMTSICs), each of the FMTSICs coupled to the inner surface at arespective position, each of the FMTSICs corresponding to one of thevirtual buttons, each of the virtual buttons corresponding to arespective region of the cover layer, each of the FMTSICs comprising:signal processing circuitry, at least one piezoelectric micromechanicalforce-measuring element (PMFE), at least one piezoelectricmicromechanical ultrasonic transducer (PMUT) configured as a transmitter(PMUT transmitter), and at least one PMUT configured as a receiver (PMUTreceiver); (A2) configuring a haptic transducer vibrationally coupled tothe cover layer; (A3) configuring a haptic controller to drive thehaptic transducer, coupled to the touch-input sub-system; (A4)transmitting, by the PMUT transmitters of each of the FMTSICs,ultrasound signals towards the cover layer; (A5) outputting, by the PMUTreceivers of each of the FMTSICs, voltage signals (PMUT voltage signals)in response to reflected ultrasound signals arriving from the coverlayer; (A6) converting, by the signal processing circuitry of each ofthe FMTSICs, the respective PMUT voltage signals to PMUT digital data;(A7) outputting, by the PMFEs of each of the FMTSICs, voltage signals(PMFE voltage signals) in accordance with a time-varying strain atrespective portions of a piezoelectric layer at the respective PMFEsresulting from a low-frequency mechanical deformation; (A8) converting,by the signal processing circuitry of each of the FMTSICs, therespective PMFE voltage signals to PMFE digital data; (A9) determining,by the touch-input sub-system, supplemental haptic feedback commands if“PMUT Triggered” Boolean data is True for at least one of the FMTSICs(Touched FMTSICs) and light-force conditions are satisfied for all ofthe Touched FMTSICs; (A10) determining, by the touch-input sub-system,primary touch inputs if “PMUT Triggered” Boolean data is True for atleast one of the FMTSICs (Touched FMTSICs) and light-force conditionsare not satisfied for at least one of the Touched FMTSICs; and (A11)driving the haptic transducer to generate haptic feedback in accordancewith the supplemental haptic feedback commands, the haptic feedbackgenerated in accordance with supplemental haptic feedback commandsdelineating a location of at least one of the virtual buttons; whereinthe light-force conditions of each of the FMTSICs comprise: the PMFEdigital data of the respective FMTSIC indicates an applied force lessthan a light-force threshold F_(light); and the “PMUT Triggered” Booleandata are obtained from the PMUT digital data.
 21. The method of claim20, wherein there are two or more FMTSICs corresponding to each of thevirtual buttons.
 22. The method of claim 20, wherein the light-forcethreshold F_(light) is 150 grams-force or less.
 23. The method of claim20, additionally comprising: (A12) determining, by the touch-inputsub-system, primary haptic feedback commands if “PMUT Triggered” Booleandata is True for at least one of the FMTSICs (Touched FMTSICs) andlight-force conditions are not satisfied for at least one of the TouchedFMTSICs; and (A13) driving the haptic transducer to generate hapticfeedback in accordance with the primary haptic feedback commands. 24.The method of claim 23, wherein haptic feedback generated in accordancewith primary haptic feedback commands and haptic feedback generated inaccordance with supplemental haptic feedback commands are noticeablydifferent in one or more of the following: amplitude, frequency, andpattern.
 25. A method of delineating a location of a virtual button byhaptic feedback, comprising: (B1) configuring a touch-input sub-systemcomprising a cover layer having an outer surface, which can be touchedby a finger and an inner surface opposite the outer surface, and aplurality of force-measuring and touch-sensing integrated circuits(FMTSICs), each of the FMTSICs coupled to the inner surface at arespective position, each of the FMTSICs corresponding to one of thevirtual buttons, each of the virtual buttons corresponding to arespective region of the cover layer, each of the FMTSICs comprising:signal processing circuitry, at least one piezoelectric micromechanicalforce-measuring element (PMFE), at least one piezoelectricmicromechanical ultrasonic transducer (PMUT) configured as a transmitter(PMUT transmitter), and at least one PMUT configured as a receiver (PMUTreceiver); (B2) configuring a processor coupled to the touch-inputsub-system; (B3) configuring a haptic transducer vibrationally coupledto the cover layer; (B4) configuring a haptic controller to drive thehaptic transducer, coupled to processor and optionally coupled to thetouch-input sub-system; (B5) transmitting, by the PMUT transmitters ofeach of the FMTSICs, ultrasound signals towards the cover layer; (B6)outputting, by the PMUT receivers of each of the FMTSICs, voltagesignals (PMUT voltage signals) in response to reflected ultrasoundsignals arriving from the cover layer; (B7) converting, by the signalprocessing circuitry of each of the FMTSICs, the respective PMUT voltagesignals to PMUT digital data; (B8) outputting, by the PMFEs of each ofthe FMTSICs, voltage signals (PMFE voltage signals) in accordance with atime-varying strain at respective portions of a piezoelectric layer atthe respective PMFEs resulting from a low-frequency mechanicaldeformation; (B9) converting, by the signal processing circuitry of eachof the FMTSICs, the respective PMFE voltage signals to PMFE digitaldata; (B10) determining, by the touch-input sub-system or the processor,supplemental haptic feedback commands if “PMUT Triggered” Boolean datais True for at least one of the FMTSICs (Touched FMTSICs) andlight-force conditions are satisfied for all of the Touched FMTSICs;(B11) determining, by the touch-input sub-system or the processor,primary touch inputs if “PMUT Triggered” Boolean data is True for atleast one of the FMTSICs (Touched FMTSICs) and light-force conditionsare not satisfied for at least one of the Touched FMTSICs; and (B12)driving the haptic transducer to generate haptic feedback in accordancewith the supplemental haptic feedback commands, the haptic feedbackgenerated in accordance with supplemental haptic feedback commandsdelineating a location of at least one of the virtual buttons; whereinthe light-force conditions of each of the FMTSICs comprise: the PMFEdigital data of the respective FMTSIC indicates an applied force lessthan a light-force threshold F_(light); and the “PMUT Triggered” Booleandata are obtained from the PMUT digital data.
 26. The method of claim25, wherein there are two or more FMTSICs corresponding to each of thevirtual buttons.
 27. The method of claim 25, wherein the light-forcethreshold F_(light) is 150 grams-force or less.
 28. The method of claim25, additionally comprising: (B13) determining, by the touch-inputsub-system or the processor, primary haptic feedback commands if “PMUTTriggered” Boolean data is True for at least one of the FMTSICs (TouchedFMTSICs) and light-force conditions are not satisfied for at least oneof the Touched FMTSICs; and (B14) driving the haptic transducer togenerate haptic feedback in accordance with the primary haptic feedbackcommands.
 29. The method of claim 28, wherein haptic feedback generatedin accordance with primary haptic feedback commands and haptic feedbackgenerated in accordance with supplemental haptic feedback commands arenoticeably different in one or more of the following: amplitude,frequency, and pattern.
 30. A method of determining user-input,comprising: (C1) configuring a touch-input sub-system comprising a coverlayer having an outer surface, which can be touched by a finger and aninner surface opposite the outer surface, and a plurality offorce-measuring and touch-sensing integrated circuits (FMTSICs), each ofthe FMTSICs coupled to the inner surface at a respective position, eachof the FMTSICs corresponding to one of the virtual buttons, each of thevirtual buttons corresponding to a respective region of the cover layer,each of the FMTSICs comprising: signal processing circuitry, at leastone piezoelectric micromechanical force-measuring element (PMFE), atleast one piezoelectric micromechanical ultrasonic transducer (PMUT)configured as a transmitter (PMUT transmitter), and at least one PMUTconfigured as a receiver (PMUT receiver); (C2) configuring another inputsub-system; (C3) configuring a processor coupled to the touch-inputsub-system and to the other input sub-system; (C4) configuring a haptictransducer vibrationally coupled to the cover layer; (C5) configuring ahaptic controller to drive the haptic transducer, coupled to theprocessor and optionally coupled to the touch-input sub-system; (C6)transmitting, by the PMUT transmitters of each of the FMTSICs,ultrasound signals towards the cover layer; (C7) outputting, by the PMUTreceivers of each of the FMTSICs, voltage signals (PMUT voltage signals)in response to reflected ultrasound signals arriving from the coverlayer; (C8) converting, by the signal processing circuitry of each ofthe FMTSICs, the respective PMUT voltage signals to PMUT digital data;(C9) outputting, by the PMFEs of each of the FMTSICs, voltage signals(PMFE voltage signals) in accordance with a time-varying strain atrespective portions of a piezoelectric layer at the respective PMFEsresulting from a low-frequency mechanical deformation; (C10) converting,by the signal processing circuitry of each of the FMTSICs, therespective PMFE voltage signals to PMFE digital data; (C11) determining,by the touch-input sub-system or the processor, zeroth supplementaltouch inputs if “PMUT Triggered” Boolean data is False for all of theFMTSICs; (C12) determining, by the touch-input sub-system or theprocessor, first supplemental touch inputs if “PMUT Triggered” Booleandata is True for at least one of the FMTSICs (Touched FMTSICs) andlight-force conditions are satisfied for all of the Touched FMTSICs;(C13) determining, by the touch-input sub-system or processor, primarytouch inputs if “PMUT Triggered” Boolean data is True for at least oneof the FMTSICs (Touched FMTSICs) and light-force conditions are notsatisfied for at least one of the Touched FMTSICs; and (C14)determining, by the processor, combined inputs in accordance with (1)primary inputs from the other input sub-system and (2) the zerothsupplemental touch inputs or the first supplemental touch inputs;wherein the light-force conditions of each of the FMTSICs comprise: thePMFE digital data of the respective FMTSIC indicates an applied forceless than a light-force threshold F_(light); and the “PMUT Triggered”Boolean data are obtained from the PMUT digital data.
 31. The method ofclaim 30, wherein there are two or more FMTSICs corresponding to each ofthe virtual buttons.
 32. The method of claim 30, wherein the light-forcethreshold F_(light) is 150 grams-force or less.
 33. The method of claim30, additionally comprising: (C15) determining, by the touch-inputsub-system or the processor, supplemental haptic feedback commands if“PMUT Triggered” Boolean data is True for at least one of the FMTSICs(Touched FMTSICs) and light-force conditions are satisfied for all ofthe Touched FMTSICs; (C16) determining, by the touch-input sub-system orthe processor, primary haptic feedback commands if “PMUT Triggered”Boolean data is True for at least one of the FMTSICs (Touched FMTSICs)and light-force conditions are not satisfied for at least one of theTouched FMTSICs; and (C17) driving the haptic transducer to generatehaptic feedback in accordance with the primary haptic feedback commandsand the supplemental haptic feedback commands.
 34. The method of claim33, wherein haptic feedback generated in accordance with primary hapticfeedback commands and haptic feedback generated in accordance withsupplemental haptic feedback commands are noticeably different in one ormore of the following: amplitude, frequency, and pattern.
 35. The methodof claim 28, wherein the other input sub-system comprises one or more ofthe following: image sensor, gyroscope, microphone, touch display panel,infrared (IR) sensor, temperature sensor, humidity sensor, pressuresensor, compass, keyboard, and joystick.